tool to get PIDS of process accessing a table

We are running informix online 5.10 and want to be able to kill all users that are accessing a particular table so that we can perform an alter table without having to bounce the engine. tbstat -k combined with tbstat -u (and a select of partnum from systables) can provide the PIDS for processes with locks, but for processes accessing the table without a lock the only information provided is tbstat -t which simply gives a user count (have I missed anything?) Is there a tool out there that can show that information for online 5 or is there documentation about informix 5 shared memory so that such tool could be written? any help greatly appreciated thank you Xavier Trevisani