limiting framerate of outside app

I am currently working on a project that requires image recognition, im looking at the output of another program (which generates bitmaps) and setting variables based on what my app sees in the image. My problem is that the application I have to look at makes frames as fast as it can, generating a framerate of 400 FPS which eats up all my processing power. I only need like 50 FPS but i dont have access to the code of the output application so i cant set a limit there.

Can anyone think of a way to limit the framerate of the application?

thanks in advance,
Glyptar

The only way I can think of accomplishing that is to set the processor priority of your app higher than the target app, and then code in such a way that your program uses up all the processor and then pauses just long enough for the other app to generate one frame, capture that frame, etc.