
I'm running a game (TORG) that uses a similar mechanic to the Shadowrun exploding dice. However, the character re-rolls 10's and 20's on a d20 (instead of just 20's) and adds all the rolls together as a single roll. Example: a roll of a 20, then a 10, then a 17 is a single roll value of 47. I won't get into the translation of the roll to a bonus number, since I don't think the program will be able to do that without serious macro programming - correct me if I'm wrong, though.