Sending MAVLink Commands / Arduino -> Pixhawk


i got a Arduino Developement Board as a companion computer with my Pixhawk driven Quad.
Now i want to send commands (exactly: RC_Channels_Override #70) generated by the Arduino to the Pixhawk.
The Arduino is programmed by LabView with use of their special Arduino compiler.
I have to generate the command signals as well with LabView programming.
Unfortunately, i cant find any examples of the string i have to generate…
Can anyone help me with this?

best regards