use this
function show(a,b) {
document.getElementById(a).style.display = "block";
document.getElementById(b).style.display = "none";
}
function hide(a,b) {
document.getElementById(a).style.display = "none";
document.getElementById(b).style.display = "none";
}
function control()
{
if(document.form.approve[0].checked == false && document.form.approve[1].checked == false)
{
alert('choose selection');
return false;
}
if(document.form.approve[0].checked == true && document.form.txt1.value == '')
{
alert('write something to txt1');
return false;
}
if(document.form.approve[1].checked == true && document.form.txt2.value == '')
{
alert('write something to txt2');
return false;
}
}
<cfform action="test.cfm" method="post" name="form" id="form" onsubmit="return control();">
<cfinput type="radio" name="approve" value="1" onclick="show('d0','d1'); ">One<br>
<div id="d0">
<cfinput type="text" name="txt1">name<br>
</div>
<cfinput type="radio" name="approve" value="1" onclick="show('d1','d0'); ">Two<br>
<div id="d1">
<cfinput type="text" name="txt2">city<br>
</div>
<cfinput type="submit" name="submit" value="Save">
</cfform>