Assuming it's B3D (that only runs when it's in the foreground), this userlib declaration should work:
.lib "user32.dll"
u32_GetForegroundWindow%():"GetForegroundWindow"
There are other (perhaps more exact) ways, of course, using functions in user32.dll, but that was just one off the top of my head.
.lib "user32.dll"
u32_GetForegroundWindow%():"GetForegroundWindow"
There are other (perhaps more exact) ways, of course, using functions in user32.dll, but that was just one off the top of my head.