Hello Asher,
just from the top of my head: as Top Secret currently does not support your request, it depends from your specific circumstances to find a feasible approach.
(1) one possible approach I already sketched in my previous post, to implement the program only in that lpar, where it is to be called. (SYSE)
(2) maybe TSSINSTX (Top Secret Exit) offers the possibility to extend the security according to your need. (Probably Performance-disadvantage, because this code would be executed for every program invocation)
(3) If you have the possibility to modify program xxxxxxxx, you could add a user security call (TSSAI or RACROUTE) at the beginning of program xxxxxxxx, to handle your needs.
(4) If your program xxxxxxxx is called within a specific facility, and it is possible to implement this facility in system SYSE only, you could use that option to implement the desired restriction.
Hope that helps a little, best regards, Josef