If you fancy this grown-up look, here's an outfit I made for inspiration:
You could also do it the other way around by wearing a jewel coloured, satin skirt with a formal top to get the look of hijabi style icon Sheikha Mozah of Qatar:And staying with Sheikha Mozah's wonderful look, I loooove this next outfit! It's young, fun and perfect for a formal college dinner:
Another idea is to wear a maxi dress of your choice and glam it up heels/wedges, a jacket to make it more formal and a clutch. This look would work best if the event isn't as formal as a prom but you are expected to look smart.
This look is pretty casual but it shows you what I mean, although I would give the waist belt a miss myself:
If you want a more promy look, I would advise a simple evening gown coupled with a (faux!)fur bolero or different jacket/bolero/throw if fur isn't to your taste. Something like this would look cute for a more formal event where women are wearing evening gowns:
If you don't want the hassle of buying a reveling dress and then hijabifiing it, I would suggest wearing a glam abaya from Iman Collections. They have recently launched a new collection of really nice abayas with a couple that are perfect for events like this. Here is my fave, at £175 it's not bad if you wear it to other events in the future:
As for the hijab, I would go for either a sophisticated Turkish style or a pretty style similar to the one below which covers the neck but still allows you to wear earrings:
I hope this helped! If you need more tips check out a post I did a while back on prom dresses, here. If you want to wear trousers instead just say and I'll do a post on it, Insha'Allah :D Have fun!