Need Multiple Stopwatch Timers on Worksheet

Not sure if this can be done but I need 70 timers on a worksheet. When data is added to a cell, the timer would start. When I highlight this cell or the station number for this cell I would like a message box to open stating the elapsed time and when the cell contents are deleted the timer would reset to 00:00. An alternative to the above would be to have the station numbers in a column on the side with the elapsed time next to it which would always be visible and if the cell is empty the timer would be 00:00. Most of the time at least 60 stations would be active. Is there a limit to the number of active timers running at one time or will this cause havoc with the worksheet? I have attached a simplified worksheet.

Appreciate any help or any suggestions how to do it better.

I think I finally solved it. Instead of using stopwatches, which I couldn't figure how to do, I just subtracted the start time from now(). I would appreciate if someone could look at the formulas etc. to see if what I did makes any sense and if it will work for about 70 stations. Another thing that I would like to do if possible is to have the "Time on Station" always running so that I don't have to keep pressing F9 all the time to update. Any comments on how to do this better will be really appreciated.

Any thoughts on this will be appreciated. Could there be a more simplified way than what I have?