Ok got an issue, i'm trying to work out how to validate a form/datobject, i have a start date for a task and an end date for the task, what i want to do is on the edit task form if the FinDate field is populated that it checks that the value is not less than the StartDate.

I've tried,

if(isset($_POST['FinDate'])) {
		 	if($_POST['FinDate'] < $_POST['StartDate']) {
            	$form->addErrorMessage('FinDate', 'End Date cannot be fore start date', 'bad');
            	return $this->redirectBack();
            }
		}

but this just keeps firing when no date is added and if a date is added it doesn't validate.

Any help or pointers much appreciated.

Mick