Excel VBA macro: How to implement running clock

Following video demonstrates how to implement simple VBA macro showing running clock in Excel worksheet. My solution has three macros:

• RunClock: Sets cell (A1) value to current time by using Now()-function. Then it recursively calls itself in every one second until global variable clockOn = FALSE. 
• StartClock: Sets global variable clockOn = TRUE and calls RunClock
• StopClock: Sets global variable clockOn = FALSE

Recursive call is made using Excel's function

Application.Ontime(EarliestTime, Procedure, LatestTime, Schedule) 

In this case only first two parameters are needed:

• EarliestTime: Time when Procedure is been run. In this case Now + TimeValue("00:00:01")
• Procedure: The name of the procedure. In this case RunClock itself 

If you want to create buttons for starting and stopping a clock, please check how to add button

Tip: If you have difficulties to see the video, try to maximise it from lower right corner: