Thanks a lot poita. I took some test shots and I agree that the Flash should provide better results. I did some research and gave it lots of thought so far, and here is my current plan...

I am going to do something like this: http://photos.imageevent.com/sipphoto/samplepictures/Slide%20Macro%20Setup.jpg

I will get one of these to detach the flash from my camera: http://www.amazon.com/gp/product/B002Z3H36O/ref=ox_sc_act_title_2?ie=UTF8&psc=1&smid=A17PX87GQZ7MWI

and one of these diffusers to put on the flash: http://www.amazon.com/gp/product/B003Y0CXX0/ref=gno_cart_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

And I will mount (maybe with superglue) the slide holder to the diffuser. You can see my slide holder on the left of the scanner in this picture: http://tinypic.com/view.php?pic=2elxhep&s=7

I have two tripods, so I will mount the flash to one, and the camera to the other. Once I get it lined up, I will use my remote trigger to take the pictures.

I may also put a tube made from posterboard or a paper towel tube between the lens and the film to block out the surrounding light and keep them stable when I slide the film through. I first need to figure out which lens is best and what the distance will be.