Find Ok code for Approve/Reject button in Form step workflow

Dear Gurus,

Can anyone tell how to find out OK Code for the "Approve" and "Reject" button in work flow form step?

I want to carry out specific function on "Approve" button but i don't know how to use this "Approve" button in IF conditions. In normal screen that we make in screen painter, we can simply do it by using OK code. But i am unable to find Ok code for this approve button? Kindly Help.

Thanks