Just a quick comment on the process, not the query...
Unless you've taken the full backup WITH CHECKSUM, the verifyonly verifies very little of the backup and can easily verify as valid a backup that won't restore. If you're going to depend on RESTORE VERIFYONLY, you need to ensure that all the backups are taken WITH CHECKSUM, even then it's not 100% certain.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability