JavaScript/Submit Button ?

[crptcblade]

<SCRIPT language=javascript> 

function fncCheckLetter() 
{ 
if(window.formLetterData.cboLetterType.value=="") 
{ 
// User did not select an item from the list. 
alert("You must pick a valid item."); 
return false;
}
else
{
  return true;
}

} 
</SCRIPT> 

<form onSubmit="return fncCheckLetter()">
<INPUT id=btnSubmitLetter name=btnSubmitLetter type=submit value=Submit tabIndex=1 >
</form>

that should work