disable all form buttons in a given duration?

I have a form in C# which has 4 buttons. I would like to disable all 4 buttons after a given duration of time, for example in 1 or 2 minutes. I searched in Google and found this code but it does not seem to work:

private System.Timers.Timer aTimer = new System.Timers.Timer(60) { AutoReset = false };
 protected void Timer2_Tick(object sender, EventArgs e) 
{     aTimer = new System.Timers.Timer(60);
 aTimer.Interval = 60; double counter = aTimer.Interval;
 counter++; if (counter >= 60) {
 lib_bt.Enabled = false;
 MessageBox.Show("Time Up!"); 
}
}