Combining cell data based on matching multiple fields.

I'm not sure if this is possible. I am trying to add dollar amounts in columns based on duplicate values in other multiple fields. I have 30+ clients that report sales weekly. If the same client makes more than one sale to the same customer, I'm wanting to total the sale. I have no idea if that is clear or enough information. SUMIFS means I have to define the value of the duplicate, but I want it to combine values based on finding duplicates. Any ideas?