Are these different fields in the same table? (That might not be your best possible table design)
If so, Sum (Quarter1, Quarter2, Quarter3, Quarter4) / Count(Quarter1, Quarter2, Quarter3, Quarter4)
For the count function to give the expected result, Unused fields must be blank, not zero.
Yes they are; I tried your solution and it works like a charm! Thank you so much!
Of course, you could also use:
Average ( Quarter1 ; Quarter2 ; Quarter3 ; Quarter4 )
but why do in one step what can be done in two?