Task priority?

How to change compiled .exe task priority via code?(the one you change by task manager)
When I hit F5 I need to have what i see to have higher priority...and how could I change a running process priority?
i'm using getdesktop function to capture a Direct3d windowed application screen..but this application takes too much CPU power to let me do getdesktop() copy operations, so I need to have my compiled exe with much priority.
Or may be there's a way to grab the d3d application screen only, without getdesktop()?
And what if I would need to send keys input to this application?
thx :)

Not so clear to me ... but Iguess it's Blitz3D app which is taking all the cpu time. One workaround is to include a delay in your main loop, or to use frame limiting ... to reduce the cpu time of the Blitz3D exe, releasing some ressources for other processes.

If you want to have higher priority for your Blitz3d exe, I don't know the solution, and I doubt that it's possible, since Blitz3d runs as fast as it can and gets the "higher priority" it can have (quite normal behaviour for a game).

Changing priority: WinAPI (-> DECLS)

Sending key input normally is useless as apps won't react to key events when out of focus.