RECOMX was included in some versions of the installation package in [7,376]. If you don't have it, you can get it here:
http://www.microsabio.net/dist/50rel/dsk0/007376/ (You'll want to grab the .bp source as the switches are set up there - thus this is a utility that you probably want to customize for your needs.) I renamed the .RUN to .LIT (which you can do too) in order to be able to run it without saying "RUN RECOMX", but that's a minor point.
The syntax then is simply:
.RECOMX
or
.RUN RECOMX
I should also point out that /X:2 is not a replacement for /M. I would retain the /M and just add the /X:2.