auto change screen area 800x600 pixels

I am looking at an API coding how to auto set user screen area to 800x600 pixels when my application
is running, resume to original setting when exit program.

Anyone can kindly post it out.

Thanks

This module will do the changing part.
Stand by, there's more coming...

This will get the current color depth...

And I think this is correct for getting the current screen resolution:

Screen.Width / 15
Screen.Height / 15

I have combined the above into one module with 3 public functions:

SaveCurrentSettings
ChangeRes
RestoreOldSettings

Here it is: