CDEF Calculate Azimuth angel from Relative Azimuth & Heading

[wkuess]

Hello,

This is my first post here at Cacti Forums,

I work with VSAT antennas, and from a few VSAT systems on the market you can get AGC value (Signal) Azimuth, Elevation and other data
from the antenna controller via SNMP.

The current antenna type I'am working with will only provide the heading of the vessel, and the Relative Azimuth. But I would like
to also graph the Azimuth also.

It's quite simple, REL+HEADING = AZ but if AZ is more than 360 then you should subtract 360.
I was wondering if I could do this in a CDEF Custom String.