Sorry, I was showing a percent, and incorrectly, I was very tired this morning...
What I was suggesting is that you create 2 running total (RT) fields which get the minimum and maximum dates for your date field (I'll call them RTmin and RTmax). You'll also want a running total field which contains the sum of your values I'll call it RTsumvalue).
Now that you have these, you can determine the number of months using the datediff function on the 2 RT date fields in a new formula, datediff returns the difference between 2 dates, in thsi case we ask for months.
Use Insert->Field Object to create formulas or RT's, and create a new formula to hold the final formula, which is:
sum(MyAvgMonthValues) / datediff('m',RTmin, RTmax)
This formula will go wherever it's need, perhaps the report footer. It's unfair to ask me where to place this when you haven't described where you've placed anything on the report.
So, you show me yours, and I'll show you...
Sorry, been a long day.
And I wouldn't call you simple or anything of the kind, not knowing Crystal well isn't what I consider a *bad* thing most days
You could also create a single formula to do all of this:
sum({YourTable.YourValueField}) / (datediff('m',minimum({YourTable.YourDatefield}), maximum({YourTable.YourYourField})))
I feared that you'd have groups and then we'd have to run through that, I generally explain this sort of thing with Running Totals to differentiate the formulas and leverage built in functionality, especially with graphical tools like the Running Totals.
-k
kai@informeddatadecisions.com