how to add additional fields to checklist item

[Phil Bradley]

Hi there, I use check list item to track training modules completed. Against each checklist item item I would like to add the following: date of completion, initials of instructor and any comments.

How can I do this please?

Thanks

Phil.

[Femke Lucassen]

only thing i can think about is automation when an checklistitem is checked, post a comment with {checklistitemname} and current date/time and username who amended the item. 
but update the checklistitem seems really complicated