What you want is pretty much a straight subsummary report. A subsummary report is based off the current found set, therefore you should perform a find for the records that you want. In this current case where the code = "SP". I would also recommend creating a calculation with date result that has a formula like: Date ( Month ( Receipt Date ); 1; Year ( Receipt Date ) ). This will take your receipt date and give it a generic first day of the month, so now you can group by that date field.
In your subsumary report, you can now group by date, then cost code. You can delete out the BODY part since you dont want any of the detail.
If you are unfamilar with subsummary reports, there a numerous examples of them on the net.