One way:

=SUM('Jan 07 Pace Final:July 07 Pace'!E7)/SUM('Jan 07 Pace
Final:July 07 Pace'!B7)


In article ,
xcel user <xcel wrote:

I hope you can help me.
I keep a monthly spreadsheet of sales numbers. each month has its own tab.
I have an average ytd column that takes the average from each subsequent
month, then adds to the current month to come up with a YTD average. As the
months go on this gets bigger and more difficult to manage.

here is an example of one formula =('Jan 07 Pace Final'!E7+'Feb 07 Pace
Final'!E7+'Mar 07 Pace Final'!E7+'Apr 07 Pace Final'!E7+'May 07 Pace
Final'!E7+E7+'June 07 Pace Final'!E7+'July 07 Pace'!E7)/('Jan 07 Pace
Final'!B7+'Feb 07 Pace Final'!B7+'Mar 07 Pace Final'!B7+'Apr 07 Pace
Final'!B7+'May 07 Pace Final'!B7+B7+'June 07 Pace Final'!B7+'July 07 Pace'!B7)

is there any way to make this more efficient and easier to use?
thanks for all your help in advance!