Calculate channel average over a specific window

Looking to find the average of a specific window of a channel. I need this to be something that can be plugged into a loop, as I'll be caclulating it on every channel (150+). Using the stat block function gets a little hairy if you try to loop it.

This is my current code, I'd like to use the average of points 98001-100001, store in variable R4, then plug into a free offset removal.

Dim iLoopOG, iLoopO, R4
  For iLoopOG = 1 to GroupCount
  For iLoopO = 2 to GroupChnCount(iLoopOG)
    R4 = **Looking for a line here to calculate average over window**
    Call ChnOffset("["&iLoopOG&"]/["&iLoopO&"]","["&iLoopOG&"]/["&iLoopO&"]",-R4,"free offset")
  Next
  Next