The file you speak of is a "complied" BASIC program file. Hence the extension is "*.BA"
You're searching for the "*.BAS" file, which is the source file (the non-compiled version).
You can create your own from within MicroStation.
type MACRO DEBUG
hit the enter key
But it sounds like you want to "DE-COMPILE" the BA file.
You'd have to do a search on "un-compiling BASIC files".
Note that this quest will not be an EZ search.
It's like asking to De-Code an EXE file.
You're about to cross the line of "COPY RIGHTS".
And begin to dewell in the realm of "hackers" & "crackers".
Although it sounds like you're just trying to learn something new.
I would try checking out books on BASIC (the computer language).
Sorry I couldn't offer more.
But I hope this focuses you in the right direction.
Rich