Calculating Totals

[Waterkiss]

My question is fairly simple: I have a field in the report for amount of insurance premium collected by agents. At the bottom of the report, I just want it to calculate the total of all the records in that field. I don't want to sort or group or anything like that, just need a total that will calculate each time I run the report. I have tried adding a text box but what expression do I use since I don't want to add multiple fields? Help Please!!

Thanks!!