OK, so here is what I suggest based on the conversation ...

Fields:
1. Lower range pull down menu 0.0-9.9 inclusive
2. Upper range pull down menu 0.0-9.9 inclusive
3. Radio buttons for choice of magnitude methodology:

Mw = Moment Magnitude -- This is the default

Ms = Surface wave Magnitude
Mb = Body wave magnitude
ML = Local or Richter Scale magnitude
Mc = Coda magnitude
Md = Duration magnitude
Global CMT = Seems like a different beast entirely, and I certainly don't understand it. Would this be something that should be included as an option somehow?

I assume these scales can be converted from one to another? Anybody know?

Rules:
1. Upper mag range must be equal to, or greater than, lower mag range.

Thoughts?