do you really need to send keyboard shortcuts? or would sending something like:
mc14.exe /mcc 10000,0
also work. this is the command for play\pause..
http://wiki.jrmediacenter.com/index.php/Media_Center_Core_Commandsits by far an easier way.
if not, open the link from above, search for what you want, and open on your computer the resource.xml you find in C:\Programme\J River\Media Center 14\Data\Default Resources (or something like that), to see if there is the command is used and what keystrokes it reacts to. the keyboard commands start about halfway of that file.
now this is complex, but the good news is that it is possible to change or add commands to the keyboard. just dont do it in there. you might want to do a forum search for how to do that, or the wiki. and when you have problems there, just ask....
gab