I'm making use of NOW() function at many places in my spreadsheet, which is basically a checklist document.

So my requirement is that for each step, it should record the datetime at which that step was completed. But whenever the Now() is being used... all the previously updated cells withe datetime are also getting updated again. Hence at the end of the day, am not able to get the detailed time at which each of those steps are completed.

This is how I've created as of now:

• Used a Checkbox for each step. Once the step is complete, on clicking the Checkbox, it will update the cell A1 as "Completed".

• In the cell B1, I've put the following function which will check for the value in A1. If it is "Completed", then it will update the value of B1 with the current datetime using Now()

  =IF(A1="Completed";NOW();"")
  

Please let me know a solution for this. Also if there any other alternative.