Averaging values

[RUSH2CROCHET]

Hello everyone:

Hoping someone can assist...

I have a spreadsheet which reflects copier meter clicks as reported from
1'08 through current day. My salesperson is wanting to determine the 3rd
qtr, 2008 vs. 3rd qtr 2009 average meter clicks.

Each month contains a rolling total. For instance:
Col H)-June '08 data= 118,992
Col I)-July '08 data= 129,406, so July meter clicks would be 10,414
Col J)-Aug '08 data= 136,904, so Aug meter clicks would be 7,498
Col K)-Sept '08 data=143,173, so Sept meter clicks would be 6,269
Col L)-3 month average would be: 24,181

The data continues through September '09, although in some months, there
will not be a value, as the machine was removed. I tried calculating monthly
differences just by inserting colums, but of course that gives me negative
values if the unit was removed, and no meter read was provided.

Any assistance you can provide would be greatly appreciated!

TIA,
Sandi

 

[Sean Timmons]

=if(OR(H2=0,I2=0),"",I2-H2)

should get you there.

If either current or previous month is 0, then leave it blank, thus avoiding
including in the average.