Forms :: Enable A Button - Capture Trigger That Fires On Pressing Exit

I have a situation where one form calls another. I am opening the other form(say B) using the below code.

declare
temp_form formmodule;
begin
temp_form := FIND_FORM ('D:RSSQ2TestingpurposesMODULE3_MULTIPLE');

[code]...

On Form B there is an Exit button on click of which it closes the Form B and returns to Form A

begin
close_form('MODULE3_MULTIPLE') ;
end;

In my scenario on Exit from FORM B i need to enable a button on FORM A.I am not able to capture the trigger that fires when I Press the Exit