how to capture mouse mid_button_click?

how to capture mouse mid_button_click?
request:
a program is hide,when i click my mouse mid_button, and it will show.

If you are not clicking the button when the mouse is on top of the form then you will have to use a system hook (you'll need a standard dll with the hook procedure).

:o :o :o :o :o :o :o :o :o
i downed a source code.
when i run it,my ACDSee cann't run!!!
but when i run my ACDSee, the code can run!
i want run it and my ACDSee!how to do?
i post the code.
help me!