Finding char in string - not from starting position

InStr ( ([comma]+1) , [Match_addr] ,",")

this is compared to finding from starting position

InStr ( ([Match_addr] ,",")

NOTE! for some reason, InStr ( ([comma]+1) , [Match_addr] ,",")
would NOT work without the +1. It will also work with a simple integer, but a field seems to require the plus modifier? Minus also didnt seem work.