adding of a pushbutton on SAP std program

Hi,

I want to add an extra pushbutton on a sap program screen. What are the steps involved for it?

There is no BADI / exit avaliable for it. I have requested OSS key for the screen object and PAI Module.

But do I need to do anything in PBO ?

Basically, I want my fuctionality when that pushbutton is pressed by user.

Thanks and rgds,

Rupalee.