Formula to calculate two fiscal year/period difference for non null quantit

Question

We'd like to have a query result like the following:
Person -- Jan_2007 -- Feb_2007 -- Mar_2007  --  No. of Months
Tom --- 21 --- 54 --- 10 --- 2
John --- 0 ---  3 --- 15 --- 1  
In the above query, the row is sales persons, the 1st three columns list the sales quantity by each sales person restricted by fiscal year/period and we would like to create 4th column "No. of Months" to calculate (will use formula) the month span (difference) for each sales person from his last sale activity (the last month he performed sales) and the 1st sale activity (the first month he performed sales) as listed in the above query result, e.g.,  Tom performed his first sales (sales quantity: 21) in the month of January of year 2007, and he performed his last sales (sales quantity of 10) in the month of March, 2007, then the "No. of Months" column value for Tom is 2.  The calculation formula will be performed based on the last quantity value (> 0) to trace it's corresponding column fiscal year/period value (max of the fiscal year/period value with quantity value >0) and on the 1st quantity value (>0) to trace it's corresonding column fiscal year/period value (min of the fiscal year/period value with quantity value >0) and then do the subtraction between the max of the fiscal year/period value and the min one. 
Would be appreciated if BEx experts here give the detailed steps on how to build up this formula to calculate the number of month difference and we will give you reward points!
Edited by: Kevin Smith on Mar 18, 2008 1:47 PM

Answer 1

hi Danny,
I only gave an example of 3 columns, but actually, yes, the report can have more than 12 months, e.g. from Jan_1999, Feb_1999, ..., Mar_2011, Apr_2011.
In our simple example of 3 columns for the three consecutive months, if John had (3)(0)(15), then the No. of Months is 2, or the last month value he performed sales and 1st month he performed sales.
You said macro in Excel sheet?  Not sure if macro will work on web since we will eventually run the reports on web browser, therefore we still prefer using Formula.
Any idea/solution?
Thanks!