DBI Function Calls

I am having difficulty understanding how to make direct calls to the
BDE function calls. Specifically, I'd like to call DBIOpenUserList to
determine who is using  a database. Can anyone direct me to some
sample code for making these calls? I've looked throught the
DBIPROCS.INT file, but I don't understand how to setup to make the
call and then extract the data afterwards.

Thank you,
Keith