Material editor - not enough "slots"...

Hi all,

A while ago some of you inhere were very kind to help me getting started 
with 3D Studio - so now I really hope you can help me again :o)
I need more free "slots" in my material editor. I now have 24 available 
slots in my material editor (I think this is standard) - but I tend to use

them all very fast - as I work on rather large projects (building houses, 
castles etc...) - Is it possible to get more available slots for different

materials? Or am I stuck with only these 24?

I hope you have an idea.

Thanks - John :o)