[Help] sheet calculation of critical failure:

So I use a custom ruleset which has players roll a save of various kinds against a fail rate they have to beat. Right now in my sheet I have the following Edit: Apparently I cant copy and paste code normally here. Ok, so what I'm looking for is how I would flag a value @{FailRate} to always flag as a critical failure. I know about the cf<X tag on dice, but since no dice are being rolled this hasn't worked on my sheet thus far.

Another way, and possibly a better outcome for what I am trying to do, would be to be able to flag critical success/failure on an equation rather than a dice roll, so: ( (@{CheckRoll} + @{CheckRoll-Mods}) - @{FailRate}) with critical success if greater than Fail Rate after that equation, or critical failure if equal or less than. Is this possible presently or should I be looking at another avenue to work out this check?