I have 12 columns (Jan-Dec) for 2007 and then 12 more columns (Jan-Dec) for
2008.

At the end of each years section of monthly columns I have a Month to Date
Difference column that compares the accumulated months for 2007 to the same
number of months for 2008.

I need a way for the formula in the MTD column to know what month I want it
to calculate to. If I am in Feb I only want it to use the 1st 2 months for
calculations by checking on the date or month I enter at the top of the MTD
column. Currently I edit the formulas so it only includes the months columns
I want. I would like this to be automatic.

A simplified example with just 3 months is shown below: I want the formula
to check the month I type into cell G1 and calulate up to the month that
matches what I typed in. The 1st example shows a 2 in G4 because that is the
diff between Jan & Feb 2007 and Jan & Feb 2008. The second example shows 3 in
G4 because that is the Diff between Jan, Feb, Mar 2007 and Jan, Feb Mar 2008:

A B C D E F G
1 Feb
2 2007 2007 2007 2008 2008 2008 MTD
3 Jan Feb Mar Jan Feb Mar DIFF
4 2 2 2 3 3 3 2


A B C D E F G
1 Mar
2 2007 2007 2007 2008 2008 2008 MTD
3 Jan Feb Mar Jan Feb Mar DIFF
4 2 2 2 3 3 3 3

Thank you