vbl tasks

[allenb@cs.uoregon.edu]

I'm trying to schedule vbl tasks from Maclisp 2.0b1, and am wondering
what the best way to get the effects of setcurrentA5 and setA5 is.
Are they, in fact, officially available somewhere, and I just haven't been
able to find the right interface file, or do I have to go to the expense of
a foreign function call?
Or, is there some relatively simple way of coding these routines in lisp?

Thanks in advance.

Allen