Just throwing in my 2 cents. A loop is going to be your best shot:

Public Function PositionOfNthOccurence (nthOccurence as Integer, SearchString as String, SearchSubString as String) as Integer
Dim i as Integer
   
   For i = 1 to nthOccurence
      PositionOfNthOccurence = Instr(SearchString, SearchSubString)
   Next 'i

End Function

Utlize the function and then in your code you only have to write the one line at least.