How to determine if the button is pressed or not in L4 Dope?

Hi all,

I am trying to write an application in L4 Dope.
Right now, I face a problem. I need to determine if the button is pressed by
user or not.
In the dope-users-guide.txt, there is a function: dope_req() . I tried to
use it to check the button event, but failed.
Is anyone know the way to figure it out? Thanks a lot.

Best Regards,
Lynette