private void txt_Sequence_KeyDown(object sender, KeyEventArgs e)
{
nonNumberEntered = false;
if (e.KeyCode < Keys.D0 || e.KeyCode > Keys.D9 && e.KeyData != Keys.OemMinus)
{
if (e.KeyCode < Keys.NumPad0 || e.KeyCode > Keys.NumPad9)
{
if (e.KeyCode != Keys.Back)
{
nonNumberEntered = true;
}
}
}
if (Control.ModifierKeys == Keys.Shift)
{
nonNumberEntered = true;
}
}