Since Prog B loops...would it be possible to have it update a data file every time it loops? At that point, you could simply pull the data created by prog B into Prog A. Of course, you might want to set Prog A to wait until the data created by Prog B has been updated AFTER the init time of Prog A.

In other words:
Set prog A to check the time when it starts. Then set Prog A to check the file date of the data file put out by Prog B. I would do that in a loop until the date/time of the data file is later than the start time of Prog A. Then we know the data is current. Then Prob A can continue on with its data. Meanwhile, Prog B continues to loop as its supposed to.

But I must state the obvious right now. You said that you want Prog A to wait for a return from Prog B. Yet you also say that Prog B is not meant to return a value. Obviously...this can't work. I assume you mean otherwise?

--Coplan