Option Explicit

Public Sub ShowMemberCount()
  Dim obj As Object
  Dim DL As Outlook.DistListItem

  If TypeOf Application.ActiveWindow Is Outlook.Explorer Then
    If Application.ActiveExplorer.Selection.Count Then
      Set obj = Application.ActiveExplorer.Selection(1)
    End If
  Else
    Set obj = Application.ActiveInspector.CurrentItem
  End If

  If Not obj Is Nothing Then
    If TypeOf obj Is Outlook.DistListItem Then
      Set DL = obj
      MsgBox "Name: " & DL.DLName & _
        vbCrLf & "Member: " & DL.MemberCount, _
        , "Member Count"
    End If
  End If
End Sub