Вы можете проверить состояние окна формы в событии изменения размера.
private void Form1_Resize(object sender, EventArgs e)
{
if (this.WindowState == FormWindowState.Maximized)
{
\\ code to execute after Maximize button has been clicked
}
if (this.WindowState == FormWindowState.Minimized)
{
\\ code to execute after Minimize button has been clicked
}
}