You will need some fields for storing the data, for example:  .datemod and .usermod.

Add these fields on a page by themselves if you do not want them to be seen.

On the blank page of an Update screen, add fields and qualifiers for the SCREEN symbols, ex: $date:

.datemod/default=$date/put=update

.usermod/default=$user/put=update

On the blank page of an Add screen, add fields:

.dateadd/default=$date/put=add

.useradd/default=$user/put=add

Or you could use the .datemod and .usermod for add or updates.  The fields would be updated each time the user writes to the record.

There is also .timemod/default= $time.