I didn't get your question clearly, but you want validation on drop down list right.. just go through this..
<select id="selctionlist" name="Answer to:">
<option>1</option>
<option>2</option>
<option>3</option>
<option>4</option>
</select>
<input type="text" /><input type="checkbox" name="c" /><br />
<input type="text" /><input type="checkbox" name="c" /><br />
<input type="text" /><input type="checkbox" name="c" /><br />
<input type="text" /><input type="checkbox" name="c" /><br />
<input type="button" onclick="validate()" /></select>
function validate()
{
var i = selctionlist.selectedIndex;
if (c[i].checked == false)
alert("Please check box" +(i+1));
}