problem with Bitmaps

[phirestalker]

I am trying to use undo in my program, so I made a class to do this (see attatched) and I put a bitmap in an instance of this class BEFORE I change the bitmap object. the function for the undo click event calls a function of the undobuf class that returns object and I cast it to bitmap and assign it to the Bitmap and then refresh the form. now, the problem is, that somehow, it is saving the changed version of the bitmap, even though I saved it before I did the change. full source for form attatched. Please help

also it will only work with 24bit bitmaps, how do I change how I use the setpixel, so that it will work with all bitmaps?