Private CtrlModiferEntered As Boolean = False

Private Sub TextBox1_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles TextBox1.KeyDown
        If e.Modifiers = Keys.Control Then
            CtrlModiferEntered = True
        Else
            CtrlModiferEntered = False
        End If
End Sub

Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
        If CtrlModiferEntered = True Then e.Handled = True
End Sub