I'm tracking my MPG's for my car. Column A has the odometer reading, B
is Gallons, C is Miles Traveled, D is MPG, and E is Average. I just
started doing this three-fillups ago, so my average right now consists
of =AVERAGE(D3:D5). If I change the "D5" to something greather than 5,
I get a #DIV/0! message. I'd rather not change that 5 to a 6 when I
want my next calculation and then to a 7 and so on. Is there way to do
this so I don't have to manually change the number each time?

Thanks.