ElfbI,
?MR2; Dwarf-style Magic Resistance
!?MR2; will work out when the game calculates dwarf-style magic resistance.
You may use !!MR and other triggers.
!!MR:N, !!MR:M works as before (described in !?MR0 and !?MR1 trigger section). The !!MR:F here is used as a percentage (0..100) of a chance for the spell to work.
Example:
ZVSE !?MR2; !!MR:F0; all creatures are completely immune to all