[mac-lisp-ide] OpenMCL debug output on arbitrary stream?

I'm not sure this is the right forum for this question; here goes anyway.

I'm still slowly working on a Cocoa back end for McCLIM. The back end is now at a stage where it can run the McCLIM Listener well enough (almost!) to be used as a tool to help development. I'd like to be able to get the break loop displayed in the Listener (this would be more convenient than switching between the McCLIM Listener and the terminal / openmcl cocoa listener when errors occurred).

However, I haven't got any ideas on how I'd achieve this. I know this is done in the OpenMCL Listener, but I can't see where.

Can anybody provide pointers on how to do this or where to look for an existing example where it's done?

-Duncan