WeakAura trigger when attempting to mount

[MHWalker]

I have little to no experience in LUA or WoW APIs, and am only experienced in making WeakAuras through the built in GUI.

I'm trying to make a simple WA that displays a custom texture and plays a sound when I try to mount (successfully or unsuccessfully), and hides after a short duration.

The texture and sound I was able to figure out, but I don't know how to set up a trigger for when I attempt to cast a mount spell (if you couldn't tell, this has something to do with being in the Maw). I'm aware of the WA someone created that tracks how many times you attempt to mount in the Maw, but I'm going for something much simpler than that, and I wasn't able to figure out how to make the trigger from their WA.

I did a lot of research on my own trying to riddle it out, and the closest I got was the UNIT_SPELLCAST_SENT event, which sounds like is what I need. I just don't know how to use it for my trigger...

Any help on this would be greatly appreciated.