Hi Alex,
Nah, no need for dynamic dll loading... unless you want to do all that.
If you want to learn about OneWorld Interoperability then I recommend you go to the Knowledge Garden and search for "OneWorld Interoperability Guide". Its a rather large pdf document, but full of good stuff. In particular, chapter 10 covers the API functions concerned with connecting to Oneworld, the exposed API's and how to call business functions.
As you will see, it is straighforward to write an app that connects to OneWorld and executes it's APIs and business functions. All you need in this case are the API's JDB_InitEnv(), JDB_InitUser(), JDE_CreateBusinessFunctionParms(), then jdeCallObject() to call the BSFN posted in the Tips and Traps forum to toggle logging..
Of course, JDE are pushing XML, Corba, COM and Java for interoperability rather than the C API's now, bit that's another story...
Have fun,
JohnO