Public Class Form1
    Dim IsLocked As Boolean = True
    Private Sub Form1_KeyDown(ByVal sender As System.Object, ByVal e As _
      System.Windows.Forms.KeyEventArgs) Handles MyBase.KeyDown
        If IsLocked = True And My.Computer.Keyboard.CtrlKeyDown And _
        My.Computer.Keyboard.AltKeyDown And e.KeyCode = Keys.Delete Then
            e.Handled = True
            Dim input As String = InputBox("Bitte geben Sie das Kennwort ein:", _
              "Kennwort")
            If input = "abc" Then
                IsLocked = False
            End If
        Else
            e.Handled = False
        End If
    End Sub
End Class