disable clicking on add to cart button if required attributes not selected

i set some attributes required, so it displays the message please select on the top of page after customess click add to cart button.

but i want the warning message display before clicking the button.

is it possible to show the message please select when mouse over the add to cart button and make the button avalable only if all required attributes selected?

thanks in advance

PS: i mean on product info page

is it possible to show the message please select when mouse over the add to cart button and make the button avalable only if all required attributes selected?
One would have to recode all of this to be interactive such as java or ajax
Can be done but is not a couple of code alterations

hi kobra,

my situation:
i dont want to refresh the page after click add to cart button, cause i use tabs on product info page, and i put add to cart button only on one tab (i dont want to show add to cart on botom of all tabs), and i also need put description on first tab.
then i get the problem, if customer clicks add to cart button without selecting attributes, the page has to be refreshed and displays please select, so it goes back to the first tab description, the customer needs to reclick add to cart tab, then select the attributes.

for zencart default create_account page, when click the submit button, an alart box pops up to remind please correct the information,
if i want the same function on product info page when click add to cart button, would it be easier to modify?
there's a file jscript_form_check.php in create_account folder, if i copy it to product_info folder, would it work? what modification do i need to make? or any other files to modify?

or any ideas? thanks