Multiple Countdown timers.

I have a small project in which I would like to create multiple countdown timers in excel however I'm fairly new to excel macros. Would love some assistance.

Basically what I'm trying to get is cells a1:a100 are usernames and b1:b100 are countdown timers. All timers would start at the same number... ex 10 mins. Could anyone help me create a macro in which I could chose a1 and that starts the countdown in b1, a2 starts b2, and so on. This would be going on at different times.This part I want to stay manual. Ie b1 starts at 8:45,b2 starts at 8:46. I would like to choose the start time of the countdown.
Point me in the right direction, send me a tutorial link, do it for me and let me learn on my own, teach me. Anything will help.

Thanks for your help in advance.
-Dawid

You should use the Application.OnTime method for this.

Maybe have some kind of start button that starts the countdown in each cell.. Ive seen it before.. not sure where or how.. but would love a tutorial is someone has one.

I looked into the: Application.OnTime Now, "my_Procedure"
However im fairy new to macros.. so I am not sure how to set up a countdown timer