vabbè va... :quipy:
codice:
Private Sub CheckBox1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox1.CheckedChanged
        If CheckBox1.Checked = False Then MsgBox("Hai deselezionato!")
End Sub
oppure:

codice:
Private Sub CheckBox1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox1.CheckedChanged
        If CheckBox1.Checked = False Then 
            MsgBox("Hai deselezionato!")
        Else
            MsgBox("Hai selezionato!")
        End If
End Sub