See (annalist) for something that has been implemented in this area.

Let EMC be the entry monitor creator.

EMC(0;SB,M,N ==> c;ME) "Create Entry Monitor"

Where N is a node or fetch key to a node containing:
slot 0 - E

slot 1 - MB

ME is a monitored entry key. Whenever ME is called, the call is recorded by a call of the form MB(order code,(byte string passed to ME); ==> ;). Then the call is passed on to key E.

Keys are not recorded. Returns from E are not recorded.

MB can be a multiplexor branch key.

C is loose end.