Extension request: Critical skill rolls

[graphil]

We have a house rule that if you roll a 20 on a skill roll then you roll again and add the result to the previous total. e.g. you have skill of 10 and you roll a 20 then another 5 so your total is 10+20+5=35. If you roll a 20 again you keep rolling.
Similarly if you roll a 1 then you roll again and subtract.

Note sure if this is even possible but is it possible to build an extension to do this automatically just like a criticial?

[Tiqon]

Quite sure it can be done, as that is how rolling in Rolemaster is handled, and it works just fine there ;). Mind you Im not capable to make such an extension, just telling you that of course it can be done :).