I would create a new table to store the data in. If you have a script to run the print you could add steps to go to the new table create a new record and set the login name and time stamp. Then have a portal on your letter layout or where you want it to show all of the record of the print jobs. this would give you better options than a repeating field in my opinion.
Can a script not fill in the other spaces of a repeating field? I was trying to avoid creating an additional table for this.
Yes a script can, but it's better to add the related table. With a related table, you can keep adding more related records as needed. With a repeating field, you will eventually fill up all your repetitions. A portal makes it very easy to list the data from that table and it's also possible to arrange that data in a row instead of a column when using what we call a "horizontal portal".
98% of the time, repeating fields are not the best design option to choose for your database.