js 单元格的问题

<%@   page   contentType="text/html;   charset=gb2312"%>   
<html>   
<head>   
<title> --表格-- </title>   
</head> 
<body>   
<script>   
var   i,j,tmp,l,r; 
var   hand1=0; 
var   hand2=0; 
  function   a(value) 
    { 
        hand1=value; 
    } 
  function   b(value) 
    { 
        hand2=value; 
    }   
//创建表格 
function   createtable()   
{   
tmp=" <table   border=1   width=5%   id   =tb1> "   
  l=document.all.txt1.value==''?0:document.all.txt1.value;   //获取文本框的值,这里我想用if-else但太麻烦 
  document.all.txt1.value=l; 
  r=document.all.txt2.value==''?0:document.all.txt2.value;   
  document.all.txt2.value=r;           if(isNaN(l)) 
                {     
                if(isNaN(r)) 
                    { 
                      alert("输入非法字符，请重新输入!"); 
                      document.all.txt1.focus(); 
                      return   false; 
                    }else{ 
                          alert("输入非法字符，请重新输入!"); 
                          document.all.txt1.focus(); 
                          return   false; 
                        } 
                } 
          if(l==0   ¦ ¦   r==   0) 
            { 
                  alert("无输入，请重新输入!"); 
                  document.all.txt1.focus(); 
                  return   false; 
              } 
for(j=0;j <l;j++)   
{   
tmp=tmp+" <tr> "   
for(i=0;i <r;i++)   
  {   
              if((hand1==0)&&(hand2==0)) 
                        { 
                              tmp=tmp+" <td   style='background:   #7B7B7B;'> "   
                              tmp=tmp+"UESTC"   
                              tmp=tmp+" </td> "           
                          } 
                if((hand1==1)&&(hand2==0)) 
                    { 
                          if(i%2==0) 
                              { 
                                    tmp=tmp+" <td   style='background:   #F9F900;'> "//   行显示黄色 
                                    tmp=tmp+"UESTC"   
                                    tmp=tmp+" </td> "   
                                } 
                        else 
                              {       
  tmp=tmp+" <td   style='background:   #7B7B7B;'> "   
                                  tmp=tmp+"UESTC"   
                                  tmp=tmp+" </td> "   
                                  } 
                        } 
                if((hand1==0)&&(hand2==1)) 
                          { 
                              if(j%2==0) 
                                  { 
                                        tmp=tmp+" <td   style='background:   #F9F900;'> "   //列显示黄色   
                                        tmp=tmp+"UESTC"   
                                        tmp=tmp+" </td> "   
                                    } 
                              else 
                                    {       
        tmp=tmp+" <td   style='background:   #7B7B7B;'> "   
                                        tmp=tmp+"UESTC"   
                                        tmp=tmp+" </td> "   
                                      } 
                            } 
                if((hand1==1)&&(hand2==1)) 
                            { 
                                if(j%2==0&&i%2==0)                 
                                  { 
                                        tmp=tmp+" <td   style='background:   #7B7B7B;'> "   
                                        tmp=tmp+"UESTC"   
                                        tmp=tmp+" </td> " 
                                    } 
                            else 
                                    {   
                                      if(j%2==0 ¦ ¦i%2==0) 
                                          { 
                                              tmp=tmp+" <td   style='background:   #F9F900;'> "   
                                              tmp=tmp+"UESTC"   
                                              tmp=tmp+" </td> "   
                                              } 
                                        else 
                                              { 
              tmp=tmp+" <td   style='background:   #7B7B7B;'> "   
                                              tmp=tmp+"UESTC"   
                                              tmp=tmp+" </td> "   
                                              } 
                                        } 
                            }       
              
}   
tmp=tmp+" </tr> "   
}   
tmp=tmp+" </table> "   
aa.innerHTML=tmp   //aa表示form的NAME 
  
}//合并单元格 
function   changetable(){ 
createtable(); 
  var   tab   =   document.all.tb1;//tb1表示表的id 
  if(tab){ 
l=document.all.txt3.value==''?0:document.all.txt3.value;   
r=document.all.txt4.value==''?0:document.all.txt4.value;   
row=document.all.txt5.value==''?0:document.all.txt5.value;   
col=document.all.txt6.value==''?0:document.all.txt6.value;   
    if(l==0   ¦ ¦   r==0   ¦ ¦   row==0   ¦ ¦   col==0) 
        { 
            alert("没输入值，请重新输入!"); 
            document.all.txt3.focus(); 
            return   false; 
                } 
      var   obj   =   document.all.tb1.childNodes(0).childNodes(l-1).childNodes(r-1); 
      if(eval(l+"+"+row+"-"+"1")> document.all.tb1.childNodes(0).childNodes.length) 
                { 
                      alert("不能合并！"); 
                        return   false; 
                    }   
      if(eval(r+"+"+col+"-"+"1")> document.all.tb1.childNodes(0).childNodes.length) 
                { 
                        alert("不能合并！"); 
                        return   false; 
                    } 
    var   tbody   =   document.all.tb1.childNodes(0); 
      for   (var   m   =0   ;   m   <eval(col+"-"+"1");   m++) 
        { 
            tbody.childNodes(l-1).childNodes(r-1).nextSibling.removeNode(); 
            tbody.childNodes(l-1).childNodes(r-1).nextSibling.removeNode(); 
          } 
    for   (var   m   =0   ;   m   <eval(row+"-"+"1")   ;   m++) 
        { 
          for   (var   n   =   0;   n <col;   n++   ) 
            { 
                indexRow   =   eval(m+"+"+l); 
                indexCol   =   eval(n+"+"+r+"-"+"1"); 
                tbody.childNodes(indexRow).childNodes(eval(r+"-"+"1")).removeNode(); 
                tbody.childNodes(indexRow).childNodes(eval(r+"-"+"1")).removeNode(); 
              } 
        } 
    with(obj) 
        { 
          colSpan   =   col; 
          rowSpan   =   row; 
        } 
    } 
      else{ 
            alert("没有表格！"); 
            document.all.txt1.focus(); 
            } 
} 
</script>   
<div   id="aa"> </div>   
<h3> 请输入要输入的表格的列数和行数： </h3>   
行:&nbsp; <input   type=text   name="txt1">   
<br>   
列:&nbsp; <input   type=text   name="txt2"> <br> 
<input   type="button"   value="提交"   onclick="createtable()">   
    <br> 
    是否隔列显示： 
    <tr> <input     type="radio"       name="radio2"   value="1"   onclick="a(1);";>   是   <input     type="radio"     name="radio2"   value="0"   onclick="a(0);"> 否     
      <br> 
    是否隔行显示： 
    <tr> <input     type="radio"       name="radio2"   value="1"   onclick="b(1);";>   是   <input     type="radio"     name="radio2"   value="0"   onclick="b(0);"> 否   
<h3> 请输入两个数字 </h3>   
<h3> 合并单元格：   </h3>   
从&nbsp;&nbsp; <input   type=text   name="txt3"> 行 <input   type=text   name="txt4"> 列开始   
<br>   
合并 <input   type=text   name="txt5"> 行 <input   type=text   name="txt6"> 列 
<br>   
<input   type="button"   value="合并"   onclick="changetable()">   
</body>   
</html> 
现在是点击合并向右合并哒.我想使其合并方向向左上方杂弄呢?请赐教...在线等..急~~~