I just did a test with Excel 2003. I opened a new Excel file (containing 3 sheets by default) and added 3 more sheets. I did not change the sheet names, so they are Sheet1 through Sheet6.
In cell A1 in Sheet1 through Sheet5, I entered a 5. Then, in Sheet6, cell A1, I entered =SUM(Sheet1:Sheet5!A1). This created the desired result in Sheet6, cell A1, which is the sum of the cell A1 in Sheet1 through Sheet5, or 25 (5x5).
I then went to cell A2 in Sheet1 through Sheet5 and entered 6. So, I need to add the formula in Sheet6, cell A2 to display the result, which would be 30. To do this, I merely copy the formula in Sheet6, cell A1 to Sheet6, cell A2. Excel updates the formula to =SUM(Sheet1:Sheet5!A2).
This should make your task much easier. Let me know if you have any problem creating your formulas or if you have further questions about the procedure.