Changing the price of an item based on quantity in Simple commerce Paypal

Hi guys

I want to know if it is possible to do that with a hooks or something like that?

My customer use simple commerce and have an item with quantity option.

I want to allow the user to put a quantity for the item and verify this quantity and ajust the price for it.

Did the hooks for simple commerce “simple_commerce_perform_actions_start()” could work but it is after purchase.

Let me know

Thank you.