Problema della sub-procedura di Applescript

Vorrei visualizzare un elenco di valori delimitati da virgole in List . Sfortunatamente, ricevo un errore che legge Microsoft Outlook got an error: Can’t continue joinList. quando tento di utilizzare la sottoprocedura che esegue il join:

tell application "Microsoft Outlook"
  ...
  set addressList to {}
  repeat with theAddress in the theAddresses
    if addressList does not contain (address of theAddress) then
      set addressList to addressList & (address of theAddress)
    end if
  end repeat

  display dialog joinList(addressList, ";") <-- error here
  ...
end tell

on joinList(aList, delimiter)
    set retVal to ""
    set prevDelimiter to AppleScript's text item delimiters
    set AppleScript's text item delimiters to delimiter
    set retVal to aList as string
    set AppleScript's text item delimiters to prevDelimiter
    return retVal
end joinList

Che cosa sto sbagliando?