Simatic: Count active acyclic jobs

Hello.

Is there a way of "asking" a CPU (S7-300/400) about how many acyclic jobs that are active?

As I understand, there is a restriction of 8 simultaneous cyclic read/write in the S7-PLC. I wonder if there is a SFC/SFB or other ways of retrieve this information from the CPU, so I can avoid "hammering" the CPU with jobs that fails. Instead I want to have an "organizer" that blocks new requests if there is 8 jobs going on at the same time.

Any ideas/thoughts about this?

Thanks
Knut

Opps! a typo sneaked in:
As I understand, there is a restriction of 8 simultaneous acyclic read/write in the S7-PLC.

tunK