I am building a price review model of top customers data.
The workbook contains 40 worksheets. Each worksheet contains the customer item transaction data sorted in Product Line Order.

Some line have 1 transaction, thereby being it's own subtotal. Some lines are 50 transactions (+/-) fr which I create a subtotal.

At the top of each worksheet I creat a customer total, which I "freeze pane" so I can scroll through below, play what if at detail level and see the anticipated changes at the op of the screen.

The problem is creating the Grand total of the sub total which can occur without a regular structure. Is there any quick way to pick these up?
At the moment I create unique Grand Total calculations for each customer which is time consuming and the boredom factor risks error.
Any help appreciated. Sincere thanks in advance.
Regards
David