screenshot code

Hi

I am trying to add a piece of software into my Visual C++ program to take a screenshot of the desktop screen several times and save the images in a folder. The program displays animated image with OpenGL

The code should be accommodated in a loop so that each time the loop is increased a function is called to take a screenshot of the movie displayed on the screen automatically and save it in a file with different name to the others, finally I would have several static image files taken at different moments and saved with a sequence of file names.

I tried to use many code I found on the web but they did not work, some of them created and saved files but could not open them and they were almost empty.

My question is: can anyone help me in this ? I need a code to be added to my program to call a function to take screenshot of my screen at specific points and save the images in different files with different names so that I can open them later with QuickTime and display them in a sequence as a movie

your help would be really appreciated

regards