You would use a label and a timer.
Declare a variable with an integer data type and make the variable hold the number you want it to start counting down from.
Then in the tick event you would do:
Dim intCountDown As Integer = 200 'The number you want to count down from here
Private Sub tmrCountDown_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles tmrCountDown.Tick
intCountDown = intCountDown - 1 'Minus 1 off the varable
lblCountDown.Text = intCountDown.ToString 'Display/update the variable in a label
End Sub
If you didn't understand what I said in my previous post then just copy the code I did above and just drag a label onto your form and call it 'lblCountDown'. Then drag a timer onto your form and call it 'tmrCountDown'.