Combining lightmaps

I know this has come up before, but after following previous posts, I couldn’t get this to work. I’m basically trying to combine two lightmaps together. In my case, this would be used to add a dynamic lightmap to a static lightmap. I know this has to be possible, but I can’t get it to work.

I’ve messed around with GL_ADD in multitexturing, with no success. Is this what I should be using? If anyone could point me in the right direction, I would be grateful. If it has anything to do with GL_ADD, please include source, since I just can’t get this to work.

Thanks in advance!