You can use the "side" function to do it all in one line, i.e.
?(side player != WEST): {_x setRadioMsg "NULL"} forEach [1,2,3,4,5]
?(side player != EAST): {_x setRadioMsg "NULL"} forEach [6,7,8,9,10]
So 1-5 are available only to west and 6-10 available only to east.