Multiple sheet sum question

[ogsl]

Hello,

I have a large, mulit-sheet document with a summary sheet. Essentially it's sales figures for multiple employees over a number of years. Each sheet represents one year, organized by salesperson (in rows) and months (in columns).

The summary sheet has exactly the same format, but obviously collates all the data from all other sheets. I'm using the =SUM('2000:2009'!A1) type sum, which is working very well in this situation.

My question is: if I wanted to find out where that specific value actually comes from (i.e. from which sheet), how would I be able to do that? It's not too bad when you just have a couple of sheets, but the document I have has over 50 so rather then flick through all of them it would be handy to be able to see the origin of the value.

I've attached an example, which hopefully will make a bit more sense.

Thanks in advance for the help!

[ncmay]

There is no RANDBETWEEN function in Excel prior to 2007.