How to stop TONOW() from updating

[Overtyped]

Hello,

I have 4 columns setup. 

Date Opened - is a created time field, logs when an entry is created
Time Opened - is a formula field with the following:  TONOW({Date Opened}) - Simply logs in minutes (will likely change to hours) how long an entry has been opened for.
Done - Simple checkmark box
Date Closed - Is a formula Field with the following: IF(Done = 1, LAST_MODIFIED_TIME(Done)) - simply logs the time an entry is marked as Done with a checkmark.

My current issue is, I'd like Time Opened to stop counting as soon as Done is checked and I cant quite figure out how to do this. Does anyone have any pointers?

Thanks!

[kuovonne · Accepted solution]

IF(

  {Done},

  DATETIME_DIFF(

    {Date Closed},
    {Date Opened},

    "minutes"

  ) & " minutes",

 TONOW({Date Opened}) 

)

[kuovonne]

If you want the time formatting in something other than minutes after it is closed, that will take a bit more work. 

You should also be aware that TONOW() does not update on a regular basis, especially if the base is closed, so it’s value is likely to be off/inaccurate.