Powerpoint-Adding Slides to presentation with Multiple Slide Maste

Hello,
I have an application which allows the user to save individual powerpoint
slides. Our system must then combine the indvidiual slides together into a
single presentation that is saved on the server.
I've run into a problem with the Slide Masters. The individual powerpoint
slides use different Master Slides. When I add a slide to the presentation
using Visual Basic Script, I end up with all the slides having the same
Master Slide as the first slide in the presentation. I want to be able to
add slides to the presentation and have the slide keep its association with
the original Master Slide. So when the slide is added to the presentation, I
need to add both the slide and the Slide Master and then have that slide
associated with the appropriate master.
Also, since more than one slide may use a given Master Slide, I don't want
to add the same master slide more than once.
Any help would be greatly appreciated.
Thanks,
Brandon