Determined updated text in Notes section in Leads screen

Hi Experts,

There is a "Notes" assignment block on Leads screen where you can enter text.

We have requirements to validate whether user text is entered in any text (multiple Text types's are assigned to lead) in note assignment block or header text based on certain status and reason code combination when user click on Save button.

I am able to read related entity(Bttext) on save method which give me 5 entries, now I am not able to figured out which entries are modified by user.

I Wanted to know if any flag or method available in BOL interface which tell me whether text is changed/modified or not.

Thanks & Regards,

Nikhil