Countdown timer Working BUT starting the timer repeatedly SPEEDS UP TIMER!

As a volunteer for a local community gym, using code cobbled from around the forums and Internet, I have a countdown timer for 10 courts in a gym where I need to be able to START STOP and RESET each court.

I could get it working but since the START triggers a new Macro, after I first START the countdown, clicking on the same START button which calls the timer subroutine results in the time being sped up!! How do I avoid that ? This is my primary and urgent problem.

I would appreciate help with three things:
1. Clicking on START button should not do anything if the timer is already running.
2. I would like to add a PAUSE button but I need a visual indicator that the countdown is paused rather than just the clock which can be hard to read.
3. I would like the start time of the countdown to be a variable that is picked from an excel cell. (right now its hardcoded at 20 minutes in the VBA code). Ideally I should be able to set a variable countdown start time for each court.

I am attaching my sheet.
Any help would be appreciated.