>What are the parameters stands for 0
>
>= mouse_event(MOUSEEVENTF_LEFTDOWN, 0, 0, 0, 0) ???

In order, they are horizontal position, vertical position, reserved, and extra application dependent message information.

The both the horizontal and vertical positions represent offset from the current mouse position, and are used to simulate movement. By setting these to 0, the mouse pointer isn't moved from its current location.

The reserved parameter is reseverd for future usage by MS. It should always be set to zero.

Lastly, the application dependent information didn't really applye, since it was done from within VFP. Normally, you'd use GetMessageExtraInfo().

hth,