How to fix a datetime in a column

[Pelaton73]

Good evening, maybe I'm missing something but I can't set a time...

Let me explain: I need to know a time when I change a precise state and then another when I press another button to be able to calculate the duration between the two events. ...

but when I press the second button the first one column is updated too... so the duration becomes zero (sigh) Can someone please explain to me how to set the time and not make it change?

Thanks to whoever will answer me and sorry for my english

[WillowMobileSys · Accepted solution]

You want to use the ChangeTimestamp type column.  It allows you specify which columns and even what values determine when the Timestamp is recorded.  

[Pelaton73]

Solved

I had the solution under my nose and I didn't notice it😬.

Thanks for your kindness and speed in replying.

I hope one day to return the favor