Ok, then try this, assuming we are talking about avi files:
1) create a dummy file "mmtest.avi" on the desktop like so: oo /n MMMPG mmtest.avi "<WP_DESKTOP>"
2) Use the context menu of that file to add "mplayer" to it as an open action. Move "mplayer" up the list to be the topmost/first action (that is: the default action)
3) now, modify the default view: oo mmtest.avi "<WP_DESKTOP>" "CLASSDEFAULTVIEW=4096;" (find out the oo switch to modify an object, I don't have that handy ...)
Maybe that will do the trick. If yes, you can then automate the process (with a REXX script) and do this for all the various file extensions that you want to have mplayer play.
