SendKeys is very powerful. You can use SendKeys to send a different keycode from the one that was pressed. For example:
private void TextBox1_KeyDown(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.Right)
{
SendKeys.Send("{TAB}");
}
if (e.KeyCode == Keys.Left)
{
SendKeys.Send("+{TAB}");
}
}
"Presses" tab when the Left or Right arrow keys are pressed.