<form>
<input name=mxh1 value="a">
<select onchange="if(this.options[selectedIndex].value!=mxh1.value) alert('请重新选择!')">
<option>请选择
<option value="a">a
<option value="b">b
</select>
</form>
<input name=mxh1 value="a">
<select onchange="if(this.options[selectedIndex].value!=mxh1.value) alert('请重新选择!')">
<option>请选择
<option value="a">a
<option value="b">b
</select>
</form>
你应该在文本框的onblur事件中添加判定代码
<input name=mxh1 value="a" onchange="if(mxh.options[mxh.selectedIndex].value!=mxh1.value) alert('输入错误!!');else alert('输入正确!');">
<select name=mxh>
<option>请选择
<option value="aaa">aaa
<option value="bbb">bbb
</select>
</form>