Automated attribute change capture


I had a query, I had created a mailto functionality for various projects based on the location for example if Project is based out in London then mail should automatically pick out the Europe mail address and so on for other countries based on region, the mailto functionality is disabled by the receiving team once the mail is triggered, manually using a boolean.

However, in the very unlikely situation of a project being shifted from location A to location B, the functionality of mailto should once again be made open to the end user. 

Currently change of location is a list formatted line item and can be easily changed by the end user, in such a scenario how do we capture/record the change and such change should therefore enable the mailto line item. 
I know this can be achieved with an action however can the same be achieved without an action as the use case isn't very likely in a practical scenario.

Appreciate all feedbacks and suggestions