' Listing 1: The nInStr Function

Function nInStr(strSource,strFind,occurrence)
  StartPosition = 1

' ******* BEGIN CALLOUT A *******
  For Findoccurrence = 1 to occurrence
    FoundPosition = InStr(StartPosition,strSource,strFind)
    StartPosition = FoundPosition + 1
    If FoundPosition = 0 Then
      Exit For
    End If
  Next
' ******* END CALLOUT A *******

  nInStr = FoundPosition
End Function