I am needing to auto increment a field based on groups within a feature class. I have 8 plots within a given polygon and I need to assign them an ID from 1-8 for each set of plots within each polygon. The polygon would have its own unique ID number to be used to group the plots.

I assume it would be an alteration of this:

    rec=0
    def autoIncrement():
     global rec
     pStart = 1 
     pInterval = 1 
     if (rec == 0): 
      rec = pStart 
     else: 
      rec = rec + pInterval 
     return rec

Thank you in advance!