While working on another project, I found the code for a custom DOSBox build at dbDOS.com. The sdlmain.cpp file puts additional items on the Win32 system menu, including a paste-from-the-Windows-clipboard feature. I've modified the code to add a help message and a menu item that launches the keyboard mapper, in case you don't want to use a keystroke to launch it.

I thought it might be useful for other people's projects, so here's the complete sdlmain.cpp file. It doesn't include the latest SVN revisions, but it may be useful. Search for "menu" and "paste" to find the additional code.