puttung together bitmaps

Well, I want to put one bitmap in to another, and so on. I'm working on a series of tiles, and rather than painting each tile individually on to the form, I want to make them all in to one bitmap, then paint them.

In theory, say I had tmpBMap, which is a bitmap object, then I have tmpBmap2 which is also a bitmap object. How would I extend tmpBmap then add tmpBmap2 to the extended tmpBMap?

 

to simply say, you want layers? I've not worked with this yet myself. I'll tell you when i figure it out.