Hi, Fazza, and thanks for your help!
I had already figured out the "=1/countif(C:C,C2)" -workaround which works fine for simple datasets but my datasets have roughly 50 columns and the users usually change the pivot table layouts quite a lot when they analyze the data. This particular case has shipment data on it and the table is being used to identify shipments from certain zip codes to certain customers by months and the costs are being calculated on the Current Way vs Suggested Way. The "Suggested way" being a specific route on nightly bases - but only for those nights when there's been shipments to these certain customers. Shouldn't be that hard a task but it is because the data may have several shipments from here to there with the same dates and some days only shipments to certain places, not all of them.
I was thinking of coming up with a some kind of SUMPRODUCT-workaround before deciding to ask for people wiser than me for some advice. There's just too many possibilities to filter the data with so I thought maybe there's an easier way...