Log changes to a field in GRID EDIT mode

I've looked up community discussions on this topic but cannot ascertain if there is a way to do this yet.

My form rules work without issues in logging changes to a field in a table. But I've received a request that users would like to add multiple records together rather than one at a time in a form. So I thought of providing a report and have them use GRID EDIT to add multiple records together. But how do I track who approved a record and when? Can I use a formula field that uses snapshot to see who modified the record when that "Approval" field changed?

Any creative way of doing this? 

Thanks

Deepa