Validation

Call a toggle function on "onclick" event of your checkbox.


function toggleValidator(chk)
{
var validatorId= document.getElementById("myValidatorId");
ValidatorEnable( validatorId, chk.checked);
}


OR  using jQuery

$('[id$=chkboxId]').click(function(){
$('[id$=myValidatorId]').attr('disabled',!this.checked);
});
and paste it inside this body to bind it when DOM is ready.
$(document).ready( function(){
.........
....
});

Hi
Right now, your just making visiblity of panel disable/enable but Validator at control is enable.
make validator disable default & when you checked the check box that time enable the validator if unchecked viceversa.

hope this helps

set causesvalidation to false
and on checkbox changed event set the dropdown.causevalidation=true