My thinking is that there isn't a way, but what you could do is use the adv btn syntax'x with custom cmds that either you watch for in the plugin or have them in the exectbl.ini file.
Bxx,xxx,xxx,xxx,xxx,"PLAY",@STOP@ (will execute PLAY on single click and STOP on hold)
Bxx,xxx,xxx,xxx,xxx,"PLAY",&STOP& (will execute STOP when pressing down and PLAY when letting it off)
And if you want it so that there has to be down for so long you could watch for the dn cmd and save the time/timer and see if long enough when the up cmd get exec'd before continuing what you want...
Hope that makes sense..