How to add form personalization on when button pressed?

I would like to add personalization in Pick Release form to call custom procedure when  EXECUTE  button is pressed.

1. How to call procedure during WHEN-BUTTON-PRESSED event?

   There is no such trigger event .  I'd like to use form personalization feature, not custom.pll

2. How to add second parameter to the procedure call , parameter is  'PICK'  ( CONSTANT VARCHAR2).

   Call is working with one parameter , when I use statement as below, but I  could not figure out how to add second parameter to procedure call from form personalization

='begin

xx_test( '''||${item.RELEASE.ORDER_HEADER_ID.value}||''');

end'