How to create a PowerPoint timer?

I have to complete a timer in PowerPoint, it counts down for a specificed amount of time when a shape on particular slide is clicked. I heard mac开发者_开发问答ros could be a way to do this, but I have very little knowledge about them. With my research I was able to add a macro and pop out a message box when a shape is clicked.

How can I implement a timer with this? VBA syntax is pretty unfamiliar to me. What happens after timer finishes is another question though.

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Ok this is a late answer but for the people coming across such task, I got over this using custom animations in PowerPoint instead of doing it with macros. There is variety of things you can do with animations so it's probably better for you to search internet for specifically what you want to do.