Steam/PC Question? Morrowwind and the tribunal expansion pack.?

I'm pretty sure I know the answer to this,

but I've been wanting to try my hand at morrowind. I've played oblivion and skyrim and I know morrowind, although won't have the same graphics, the game play is just as diverse if not bigger than it's predecessor. I saw it on steam for $19.99 USD, $20 CAN but it doesn't have tribunal =( A shame for sure. So here's my question:

If I bought morrowind for steam, and bought the tribunal expansion pack ROM online, if I tried to link the 2 games (a steam game and a non-steam game), would I be able to play the expansion pack rom even though the original game (which I would need installed in order to play the expansion packs regardless) is on the pc steam platform? I don't think it would work but I want to know as buying them together may be pricier than what's on steam. Plus, I've seen the expansion pack tribunal for super cheap. Any help would be awesome! Thanks guys! (I do want to play to meet the scandalous Barenziah and her paranoid son Helseth. Loved the story from reading it in Oblivion).