Col D = Average Col C for all rows where Col B is the same

[mikeinfl]

I have a spreadsheet that lists Technicians (Col A), their territory (Col B) and their total sales (Col C). Col D needs to be the average sales for the territory listed in Col B.

The attached example only has 6 territories, but the actual spreadsheet has 20, so my IF formula won't work and I'm not sure how to get VLOOKUP to do this.

This needs to work while the workbook is sorted via different criteria, in Excel 2003 and 2010.

Any help is appreciated.

Mike