Help!Help! MouseAPI

I want to use a API to know the current situation of right button of mouse.
I want to know it's down or it's up.
Can you tell me some solutions?
Thank you very much
:)

The situation:
The right button of mouse is "Mousedown" on a tree, then Clock event happen. The clock will to see the situation of right button of mouse every 10 ms. if the button is up then another event happen.

Thank you again

Please note one thing. The mouse will move all over the window.
I don't want to on every controlbox ,put a dragdrop event and accept mouse up event.