I don't think that you will find this exact problem solution in the Aerospace toolbox, but it does contain some functions that you will need to work this problem, specifically the ecef2lla and lla2ecef transformations.
Apart from these functions, everything else you will need are simple Euler angle to DCM calculations, which are very straightforward to do. The main thing that makes you problem complicated is that you probably want to describe the aircraft orientation relative to a local-level reference frame - this means you need to be able to perform coordinate transformations back and forth from earth to local-level and vice versa. This is what the functions ecef2lla and lla2ecef provide.
The calculation of the line of sight from the antenna to the satellite is very straightforward;
1) calculate a vector pointing from the aircraft to the satellite in the ECEF reference frame. You simply subtract the position vector for the aircraft from the position vector of the satellite.
2) rotate this vector into the local level frame (DCM ECEF to LLA) (this is the tricky one)
3) Rotate the vector from local-level to the aircraft (DCM LLA to Body made from your 3 Euler angles)
4) Rotate the vector from the body frame to the antenna frame (DCM Body to Antenna made from the antenna steering angles)
The vector now points from the aircraft to the satellite in the Antenna frame, and you can compute angles relative to the antenna.
Note that you can also construct a single [DCM ECEF to Antenna] :
[DCM ECEF to Antenna] = [DCM ECEF to LLA] * [DCM LLA to Body] * [DCM Body to Antenna]
Position Vector (Body to Satellite) in the antenna frame = [DCM ECEF to Antenna] * Position Vector (B to S) in ECEF frame.
