How in the world would you use this?
I cannot figure it out...
Well, if you are on windows NT or higher, you shouldn't use it at all.
If not, the first parameter is a combo of data. You will probably want to combine MOUSEEVENTF_ABSOLUTE with one of the events by using the | operator.
The second and third parameter will be the x and y coordinates (if you use the MOUSEEVENTF_ABSOLUTE flag then they will be screen coordinates).
The fourth coordinate should indicate which X button was pushed (normally, this is something like a 4th button on the side of the mouse, the mouse wheel, or any other miscellaneous mouse button). If you aren't sending an X button action, you should set this as 0.