You may be able to create a second account for the user as an IMAP account and tgen drag the messages from the POP account to the IMAP account on the user's desktop.
Since your backup is younger than the earliest date of the messages you are attempting to recover, you may still loose earlier messages.
Bruce Barnes
ChicagoNetTech Inc
brucecnt@comcast.net
Phonr: (773) 491-9019
Phone: (224) 444-0169
E-Mail and DNS Security Specialist
Network Security Specialist
Customer Service Portal: https://portal.chicagonettech.com
Website: https://www.ChicagoNetTech.com
Security Blog: http://networkbastion.blogspot.com/
Web and E-Mail Hosting, E-Mail Security and Consulting