Doubt regarding DateTimePicker

I have used a DateTimePicker in a windows form. I have also defined its ValueChanged event. Following is the event:

privatevoid dateTimePicker1_ValueChanged(object sender, System.EventArgs e)
{
if(dateTimePicker1.Value > DateTime.Today)
{
MessageBox.Show("Error");
}
}

I have many ways to change the date in the DateTimePicker like changing it manually or increasing the year, etc. But when I try to increment the month, using the arrow provided on the DateTimePicker to increment/decrement the month, the event is fired continuously (and not once) and I get the MessageBox recurringly. This is because the month goes on increasing (i.e. if the current month is Novemeber, the month changes to December, January, February and so on.).
Ideally, the MessageBox should have popped up only once.

Now, if I remove the MessageBox from the event, and leave the event blank, the month increases only by one if I click on the month increment/decrement button (i.e. if the current month is November, then it changes to December and stops)

Can someone explain this to me?

Regards,
Asim.

[1379 byte] By [Asim] at [2007-12-22]