I would like to calculate an average for a specific region excluding the current row.
For example, if I have the following table:
Store Units Sold Region
A 25 East
B 30 East
C 33 East
D 31 West
E 27 West
F 37 West





I would like to find that the "Remainder of Region Average" for store A is 31.5 (average of stores B and C)
Similarly, I would like to find that the "Remainder of Region Average" for store B is 29 (average of A and C)
etc...

I would want my results to look like this:

Store Units Sold Region RemainAvg
A 25 East 31.5
B 30 East 29
C 33 East 27.5
D 31 West 32
E 27 West 34
F 37 West 29