Random alphanumeric generator

Sub Test_RandomNumberLetters()
  MsgBox RandomNumberLetters(6)
    MsgBox RandomNumberLetters(6, False)
End Sub

Function RandomNumberLetters(NumberOfDigits As Integer, Optional CaseSensitive As Boolean = True) As String
  Dim i As Integer, j As Integer, ss As String, s As String
  For i = 1 To NumberOfDigits
    j = RBetween(1, 36)
    s = Chr(j + 64)
    If j > 26 Then
      s = CStr(j - 27)
    End If
    If CaseSensitive = True And j < 27 Then
      If (RBetween(1, 2) > 1) Then s = Chr(j + 96)
    End If
    ss = ss & s
  Next i
  RandomNumberLetters = ss
End Function

Function RBetween(lowerbound As Long, upperbound As Long) As Long
  RBetween = WorksheetFunction.Floor((upperbound - lowerbound + 1) * Rnd + lowerbound, 1)
End Function