LU MASTER said: Ok. Problem is, I've try to done option 1, but is not working. It doesn't even do the roll. I've change it like that for the fumble, and is working: 1d20cf20 Also, your formula does not include the threshold as a critical option. The threshold should be equal to the skill value plus modifiers. I'm starting to wandering if it's possible to do it in a simple way, since the treshold will be different for every single skill. your roll expression is not quite correct. you need to include a comparison operator (<,>, or =). e.g.: 1d20cf>20 Note that this also needs to be in inline roll brackets. For the dynamic comparison, as long as your threshold is stored on the sheet as an attribute, you can do it by just referencing the threshold attribute. As an example, if your acrobatics skill threshold attribute was acrobatics_threshold, it'd look like: 1d20cf>@{acrobatics_threshold}