Private Const WM_UNDO = &H304
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Private Sub Command1_Click()
SendMessage Text1.hwnd, WM_UNDO, 1, vbNullString
End Sub