roll20 dice help: Trying to use roll20 with Rolemaster (% dice system)

Dice question: In RM, most rolls are open ended high... and low. Roll over 95 and you get to roll again, adding the results. If the second roll is over 95, add it to the first two rolls, etc. This gives the possibility of infinitely high rolls.

But the system is also open-ended low. If you roll 1-4 (for the first roll), you roll again and subtract the second % roll. Just like above, if the second roll is 95 or greater, roll again and get a greater negative number..you have the possibility of infinitely low numbers.

Example: % roll is 56. Your roll is 56. % roll is 96, roll % again getting 34. 96+34 = 130. % roll is 96, next % roll is 98, next roll is 17. 96+98+17 = 211. (Yeah, this can happen.)

But if you start off by rolling 1 to 4 on d%.. Roll 1, then roll again applying this as a negative number. If the second roll is 96, then you keep subtracting to get a higher negative number.. to infinity, but we usually stop around +/-300.

This way, you could break a leg while jumping on your horse as it runs past you or do it so awesome that you inspire your comrades to get a bonus on their maneuvers. A grandmother could possible lift a car off a trapped child (not likely, but possible). Kill your opponent in one blow with a broken bottle or stab yourself bleeding so quickly that you die in a few rounds. My first introduction to the game was with a Mage casting Find Familiar. I fumbled so bad that he went into a month long coma.

"rolling 1d100!>95" takes care of the first part. Can I also add open ended low with the same initial /roll command?