simple textbox + toshorttimestring question

i have 2 textboxes that will log a start time and an endtime when i click on a button.


what i want to do is to have some sort of notification (a messagebox or anything else) every time the endtime = datetime.now.toshorttimestring();.
i tried this but it didnt worked:


private void Form1_Load(object sender, EventArgs e)
{

  if (endtime.Text.Equals(DateTime.Now.ToShortTimeString()))
{
MessageBox.Show("time is up");
}


}

thanks in advance.