VBS: Function & Sub

Hallo zusammen hab eine Problem ich bekomm die Variable einfach nicht von der Function in das Sub:
 

Function read_pw(ByRef rot13text_rotated)
   Set WshShell = CreateObject("WScript.Shell")
   key = WshShell.regread ("HKEY_CURRENT_USER\Software\key")
   locator = StrReverse(key)
   For i = 1 To Len(locator)
      j = Mid(locator, i, 1) ' take the next character in the string
      k = Asc(j) ' find out the character code
      If k >= 97 And k =< 109 Then
         k = k + 13 ' a ... m inclusive become n ... z
      ElseIf k >= 110 And k =< 122 Then
         k = k - 13 ' n ... z inclusive become a ... m
      ElseIf k >= 65 And k =< 77 Then
         k = k + 13 ' A ... M inclusive become N ... Z
      ElseIf k >= 78 And k =< 90 Then
         k = k - 13 ' N ... Z inclusive become A ... M
      End If


   rot13text_rotated = rot13text_rotated & Chr(k)

   Next


End Function

Sub test
   
   ttext = read_pw(rot13text_rotated)
   MsgBox ttext

End Sub