I have some financial data with months (Jan - Dec) across the top and cost
categories (such as Labor, Materials, Travel) down the side. This data is
replicated in a large number of identical worksheets (Dept A, Dept B, Dept C.,
etc).

I have a summary sheet up front and I want to do a Year to Date calculation
which for each cost category based on the current month. I have a cell in
which the current month is entered. I found a formula for YTD calculations
which works well for one worksheet:

"=SUM(OFFSET(C2,0,0,1,A1))" where A1 is the current month and the month by
month data is in C2 through n2.

How can I adapt this to work with multiple worksheets? I tried "=SUM
(Worksheet1:Worksheet25!OFFSET(C2,0,0,1,A1))" but it errored.