I want to set up a spreadsheet to sum only certain rows.

I have a list of orders (One on each row), but only some have
invoices. I would like to go through the rows and produce two sums:
One would be the sum for rows with invoices, the other for rows
without invoivces.

(The invoice reference is in one column, the ammount is in another
column)

I am trying to write a module, but am new to VB.

Thanks in advance.

Andrew