I would be very grateful for some help from an experienced user. I'm a graphic designer and I use Filemaker for client invoices. I am trying to figure out a way to create a calculation for a field that will add up all outstanding invoices. I have a "Year to Date" calculation that tells me everything that has been invoiced. When an invoice is paid, I enter the date in a "Date Paid" field. So what I need to figure out is a calculation that will add up all the invoices that have an EMPTY "Date Paid" field, and subtract them from the "Year to Date" summary field. I've now spent three days trying to do that, and I feel like a total idiot. Thanks very much for any help you can provide! Please feel free to email me at email@example.com, or post here, if you have a solution. Thanks again!