When Button Pressed
declare
begin
set_item_property('Post',enabled,property_false);
end;

go_item

-- the 1st time you click the button, IF part will be executed.
-- Next time, ELSE part will be executed, and NULL; won't do anything

if :parameter.btn_pressed = 'N' then
   -- do something here; I presume you aren't just clicking the button
   -- and it does nothing; right?
   
   -- set the parameter value so that it nows says "button was pressed"
   :parameter.btn_pressed := 'Y';
else
   null;
end if;