I haven't tested this configuration
But first of all is user does not put a tape in the first job will start and wait - it won't actually fail - to make it fail you have to use the options for timing out that are part of the selection list configuration for the job.
Once it has failed you may be able to create a rule for the failure that runs a bemcmd.exe operation (via a .cmd file) to start a named job - obviously have the job already created with B2Dspecified but not scheduled.
It might however be worth you looking into creating an e-mail reminder before the backup to tape starts (assuming it is astand alone drive anyway)
If you configure you backup jobs ot eject tape at end (or end of last job if you use a sequence of append jobs) then if the user does not insert a tape (or at least shove the existing tape back in then an inventory job will fail.)
So if you then schedule the inventory job for between when the user should have changed the tape and when the backup to tape job should start it is possible to create an e-mail alert on this job failing - that could go to yourself and the tape changing user as a reminder.
