If I understand correctly- Once a week you backup to tape the B2D location containing the *.bkf files- now you want to restore a set of *.bkf files, and restore data from them. Is that correct?
1.)On you B2D location create a folder called restore.
2.) Redirect your tape restore to this folder
3.) Create a new B2D location within backup exec pointing to the \restore folder you just restored to.
4.) Inventory and catalog the restored data. Perform the data restore through the normal restore GUI.
In the future, you would be better to create a policy that would duplicate a B2D job to tape rather than backing up the B2D location. This way you could restore data directly from tape.
If I completly misunderstood your post- please forgive me and try explainig again :)