Making multimedia the primary function of fn keys

Hey everyone,
I recently changed the function of my F2 and F3 keys to volume up and down, so now there is no need to hold down the fn key for that to be activated. However I still want to be able to assign something else to the keys for when the fn key IS held down. For instance, before this I could rename a file by just pressing down F2, and if I wanted to lower the volume I'd have to press fn with it. Now when I press F2 the volume goes down, but when I press fn simultaneously it still just lowers the volume, so I basically lost the second function of that key, which was renaming files. Is there anyway to assign something to the combination of fn + F2?
The keyboard is an Ornata Chroma, and I'm using Synapse 3.