How to ADD edited value to PREVIOUS value of SAME column/field?

[3imad_Zaynedin]

Hello,
I’m working on an app that creates simple subscription contracts. These contracts have a [StartDate] and an [EndDate], but I want to “Renew” these contracts “without” creating a new entry and i need to “log” all the start and end dates before and after a renewal. What is the best way to do so?

If anyone can tell me how to ADD the NEW value of the EDITED column to the EXISTING/PREVIOUS value of that SAME column/field i’m editing it will solve my problem.

Here’s what i tried on a TEXT column named [LogAllStartDates]:
Concatenate([_This],“”,Text([NewStartDate],“dd/mm/yyyy”)

also tried:
Concatenate([_ThisRow].[LogOfAllStartDates],“”, Text([NewStartDate],“dd/mm/yyyy”)

also tried
Concatenate([LogOfAllStartDates],“”, Text([NewStartDate],“dd/mm/yyyy”)

PS: I don’t want to use “ENUMLIST”

All failed. Please advice
Thank you