Private mUserInitiated As Boolean = True
 
    Private Sub DoSth()
        ' work, work, work ...
        mUserInitiated = False
        Me.Close()
    End Sub
 
    Private Sub Form1_FormClosing(ByVal sender As System.Object, ByVal e As _
      System.Windows.Forms.FormClosingEventArgs) Handles MyBase.FormClosing
        If mUserInitiated Then
            Dim result As DialogResult = MessageBox.Show("Wollen Sie wirklich" & _
              "das Fenster schließen", "Schließen", MessageBoxButtons.YesNo, _
              MessageBoxIcon.Question)
 
            If result = DialogResult.Yes Then
                e.Cancel = False
            Else
                e.Cancel = True
            End If
        End If
    End Sub