Party venues in Brussels

Hi! I'm in my last year of secondary school, and the end is near... I'm trying to organise my school's end of year ball, but I'm struggling to find a venue big enough to fit 70 people (not too big so we don't look ridiculous), with a bar of course. The set date is june 24th, but I have until Friday to find a great place or the rest of the commitee will just go on and book some nightclub I wouldn't set foot in ever, nevermind on this very special occasion.

It would also have to be in Brussels of course, preferably somewhere accessible.

Any ideas would be greatly appreciated :)

Natalie