Thanks very much for your help, Eric.
> In the scripts Terabyte is providing
> . . . . . .
> in osdtool.tbs
Before the first post I took a look at the scripts Terabyte ships with BIBM. osdtool isn't among them, but I doubt it would make much of a difference. The code is very sparsely commented and it branches out like a spiderweb--doubtless I'm more obtuse than most BIBM users, but I'm only able to make sense of about a quarter of their code.
Nonetheless, due to your much clearer explanations, I've now constructed a working method to achieve the goal for which this thread was started. Much gratitude. Now on to the next problem (which has no relationship whatsoever to the difficulties I was having here, so starting different thread).