=IFERROR(INDEX(RevisitsOpenOverwrite!C:C,MATCH(B2,RevisitsOpenOverwrite!C:C,0)),INDEX(RevisitsClosedAppend!C:C,MATCH(B2,RevisitsClosedAppend!C:C,0)))&"-2"

I use this to run a 2nd formula if the first one gives an error. However, there are cases where both will produce on error. In that situation I want to return a blank cell. What would be the best method for this?