HELP -- API function won't compile

[RPS]

Hi,
I'm using CYGWIN g++. I'm having trouble making an API call the
WindowFromPoint function.
Here is my code.
FILE: t.cc
#include <windows.h>
int main () {

POINT p;
p.x=200;
p.y=200;

HWND window_handle;

window_handle = WindowFromPoint(p);

return 0;
}
Here is the error message I'm getting:
C:\DOCUME~1\jeff\LOCALS~1\Temp\ccIIB5F0.o(.text+0x 22):t.cc: undefined
reference to 'WindowFromPoint@8'

Could someone please tell me
1)What this error means and
2)What I need to do to fix it
Thank you
Jeff