Try...

Code:
Private Sub Workbook_SheetSelectionChange(ByVal Sh As Object, ByVal Target As Range)
     
    Dim objArea As Object
    Dim rngCells As Range
    Dim strAddress As String
    
    If Len(Selection.Address) > 251 Then
        For Each objArea In Target.Areas
            strAddress = strAddress & objArea.Address & ","
        Next objArea
        strAddress = Left(strAddress, Len(strAddress) - 1)
        MsgBox "Len(Selection.Address) = " & Len(strAddress) & vbCrLf & vbCrLf _
            & "The address is " & vbCrLf & vbCrLf & _
            strAddress
   End If
   
End Sub