Don't laugh ... I need to write a DLM that uses Windows DDE to push and pull data from an optical design tool (ZEMAX). DDE is the only data-interface protocol that ZEMAX supports. Has anybody out there ever done such a thing? IDL has some old DDE-support functions lurking in its core, but they don't work reliably for me and they're unsupported "dark" code. I need something I can troubleshoot/expand. Thanks in advance for any info that may be lying around out there! Eric Coppock Ball Aerospace