BitBlt Function question.

I was wondering, can you use the c++ BitBlt function to capture an image of a window (not your own window, but that of another program) then use a reference image to locate where on the image the reference image is.

I'm working on a bot program, and want it to be able to detect whether a button is labeled "a" or labeled "b" and then click it accordingly(the clicking part i already got solved)

I'm using AHK for the mouse clicks,
I'm just trying to find a way to get information from the window so the program "knows" when to click.  looking at EasyBMP at the moment...
 unless AHK will take visual input too?