<form name="Add_FILE" method="post" action="downfile.jsp?AddFILE" enctype="multipart/form-data">
.....
<select name="field" onchange="location='downcenterM.jsp?field='+this.value">
</form>
.....
<select name="field" onchange="location='downcenterM.jsp?field='+this.value">
</form>
<input type="text" name="txt">
<input type="checkbox" name="chk">
<select name="field" onchange="odisabled(this.value)">
<option value="">
<option value="1">1
<option value="2">2
</select>
</form>
<script>
function odisabled(str)
{
var el = document.Add_FILE.elements;
for(var i=0;i<el.length;i++)
{
if(el[i].name!="field")el[i].disabled=true;
}
document.Add_FILE.action='downcenterM.jsp?field&field='+str;
}
</script>