Here's an alternative...

On each sheet do the following...

1) Enter your unique list of product numbers in an out of the way column. So for example if you have 10 different products, enter them in IU1:IU10 in the same order for each sheet.

2) For each sheet, enter the following formula in IV1 and copy down:

=SUMIF($A$2:$A$12,IU1,$B$2:$B$12)

Insert a new sheet, name it 'First', and make sure it's the first sheet in your workbook. Insert another new sheet, name it 'Last', and make sure it's the last sheet in your workbook.

On your master sheet do the following...

1) Enter your list of products in the same order as other sheets, let's say A1:A10.

2) Enter the following formula in B1 and copy down:

=SUM('First:Last'!IV1)

Now, every time you add a new sheet, place it between the 'First' and 'Last' sheet. Your totals should automatically be updated. Also, you can hide Columns U and V for each of your sheets.

Hope this helps!