How to link Multiple Text field to activities

Hi,

We using on-premise server 2016, On the case form a multiple text field is added and named as "Engineer Comments".

Now on the same multiple text box, multiple engineer put their comment and we unable to track who are all updating on the comment box as it is free text box.

How to track activities of this multiple text field and we want to show this text box activities log history for monitoring.

Regards

Faisal