AddToCartButton - OnClick Event?

[Chris Bond]

Really need todo the following - but can't work out how to add this to the custom controls - can someone help?

Have a AddToCartButton on a form - want to be able to add a OnClick Event to it so when its clicked it fires the event.

For example, I have a quantity dropdownlist next to it with AutoPostBack = true, on the OnClick of AddToCartButton I want to set the correct quantity.
Might seem simple but looking at the controls they dont follow the composition method of doing things with controls....

Add this event OnClick does mean we can do things with ajax too which will be even cooler.

Kind Regards,
Chris Bond