Just found a fudge dice instruction already built into the dice roller.
e.g. 2dF+4 (or 2dF-4) The dice roll used on the Fudge game system.
Rolls <dice> (default 4) dice, each of which has sides marked -1, 0 and +1, adds them up, adds <bonus> (default 0) to the result and finally multiplies by <mult> (default 1).
You might want to test this and see which format you prefer.