Numeric Operation in Rule Sets

Hi Guys,

Tell me, is it possible to perform numeric Operations like add, subtract, multiply, and divide via Rule Sets using config only? Sample is we want to compute for the net delivery quantity and store it in a single control parameter. For each delivery document that comes in, we add the delivery quantity to the net delivery quantity; and for each delivery reversal we subtract it. Let me know your comments, I prefer not putting a function module in there.

Regards,

Melvin