I have a series of sheets containing product data, each with the same
structure. In the first sheet (e.g. A_MONTH), I have monthly data. In the
second sheet (A_YTD), I calculate the year to date figures from the data in
the first sheet using a simple SUM command.

I only need to look at one product at a time and (to save space) was going
to create a single YTD sheet where the figures would be calculated for the
product being viewed by the user (this would be selected by a dropdown box).

However, I cannot work out how I can change the simple
=SUM(A_MONTH!B10:B10), etc formulas to look at the appropriate MONTH sheet
for the product that has been selected. I feel certaijn that I will need to
use a different command, but cannot work out which.

IanC