Hi Johnny,
As you will have seen, sheetspread has already given you a specific example of how to achieve what you want.
Your syntax was a bit skewey :
1. You can't AVERAGE a single cell (you just get the same value back)
2. You were using IF instead of AVERAGEIF
Whenever you need help with an inbuilt Excel Function, just use the "insert Function" button on the Formulas Tab, and then pick your function. Excel will then break up entering the formula parameters in a helpful way with explanation of what each one is. It also provides a link to "help on this function" once you've selected it.
Cheers.