Seleccionar todo el texto:
    Text1.SetFocus
    Text1.SelStart = 0
    Text1.SelLength = Len(Text1.Text)

Copiar texto:
    Clipboard.Clear
    Clipboard.SetText Text1.SelText
    Text1.SetFocus

Pegar texto:
    Text1.SelText = Clipboard.GetText()
    Text1.SetFocus

Cortar texto:
    Clipboard.SetText Text1.SelText
    Text1.SelText = ""
    Text1.SetFocus

Deshacer texto: (sólo para el control RTF)

    Declarar la función del API SendMessage :

    Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal _
    hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Long) As Long

    Para deshacer enviar el mensaje al control :

    res = SendMessage(Text1.hwnd, &HC7, 0&, 0&)
    If res = -1 Then 'hubo un error
       Beep
    End If