In reply to venkatasubbarao:
Oh, if HOLD_TIME is 0, you need ##0.
For your setup check, you need to use an implication such that when the antecedent(LHS) is true, the assertion fails.
##[0:SETUP_TIME] $changed(data) intersect $fell(strb_in) |-> 0
This may not be correct, but should get you going in the right direction.