Web Forms :: Validator To Check If At Least One Textbox Has Been Filled?

i need to check , client side, if both email and phone number are empty .The textboxes are template columns of a detailview. I've added a custom validator for each textbox (one inside edit template, one inside insert template, etc . . ) each custom validator call the same javascript function . So the problem is : the custom valiator is activated only when at least a charachter is put into a textbox and i want to check if both textbox are empty .