Take a look at the CommandRequestPacket in emptool:

#define COM_PLAYFID 3 // Start playing a specific FID.
#define COM_PLAYSTATE 4 // Play/pause the unit.
#define COM_BUILDMULTFIDS 5 // Start building a list of FIDs for playing.
#define COM_PLAYMULTFIDS 6 // Last list of FIDs for playing.

typedef struct tagCommandRequestPacket
{
EmpegPacketHeader header;
int command;
int parameter0;
int parameter1;
char parameter2[256];
} CommandRequestPacket;

I'm not sure if there is a command parameter for NEXT and PREV ... Empeg guys -- is there?

Mike