Abfragen, ob Mouse down

[Tyrael Y.]

Vielleicht hilft dir ja mouse_event aus der Win SDK weiter...

The mouse_event function synthesizes mouse motion and button clicks.

VOID mouse_event(

DWORD dwFlags, // flags specifying various motion/click variants
DWORD dx, // horizontal mouse position or position change
DWORD dy, // vertical mouse position or position change
DWORD dwData, // amount of wheel movement
DWORD dwExtraInfo // 32 bits of application-defined information
);

..guck mal weiter in der Hilfe