Countdown Timer On Userform?

how to modify, other than one piece) for a simple countdown timer to place on a userform. On my form if a user clicks a check box I display a label that shows a count down from 300 to 0 (best/simplest code I could find to modify for my purposes). But I'd rather it look like a timer counting down from "00:05:00" to "00:00:00".

Code:
Private Sub PPackCall14_Click()
'lbCountDown, lbMinutes
If PPackCall14 = True Then
Dim i As Integer
Select Case lbMinutes.Value
Case ""

[code]....