Copying cells if criteria is met

Hello,


I have multiple sheets with sheet 1 as the main sheet for entering data.
A cell for entering a order number
Cells for entering invoice no.'s for each store.
(Which coppies to the rest of the sheets. The above I've figured out with using: =IF(Sheet1!B3="","",Sheet1!B3).
but now I need to know how add total boxes into the main sheet and it automatically adds the number of boxes into the other sheets.

Please would be thankfullgreatly