Custom mavlink message

Hello everyone,
I’m using ArduPlane4.0.3 to create a mavlink message, I’ve added CUSTOM_MSG in ardupilotmega.xlm and compiled with ./waf configure && ./waf plane to get the new mavlink_msg_custom_msg.h.
I’ve also made a new function in GCS_Mavlink.cpp called send_custom_msg(mavlink_channel_t chan) which uses mavlink_msg_custom_msg_send(arguments_specified_CUSTOM_MSG_in_xml ).
my question is how to make this message appear in QGroundControl, I’ve opened an issue there and they recommended to ask here.
how to verify that the message has been sent? and using mavlink_udp.c example I’m packing the message and send it like the other messages there but still i get all the messages in the example in QGroundControl except my custom one.