Gack! You Want Me To Wear What?!

I have just discovered that my little sister's engagement party is to be a formal event.  As in, cocktail dress formal event.

For most women, this is probably not panic inducing.  (Okay, maybe a little panic-inducing.)

I don't own a cocktail dress.

I have several skirts, not all of which fit me and most of which fall into the 'casual' line.  Ditto with tops.  Some are "go out with friends to a restaurant" ready but not anything which reads as formal.

My life is fairly casual and with most of our non-mortgage-and-food money going to help the boys, buying clothes hasn't really been a priority of late (say, the last six years).  I had thought I might spring to buy some nice shoes so that I didn't have to wear my sneakers but I was not expecting to have to buy a dress for the engagement party.  (Wedding, yes.  But I'm pretty sure I can't wear the same one to both ... it's in the Girl Code.)

Now I have just over 2 weeks to make this work. 

I'm leaning towards buying a really nice formal top, something I can wear with dress pants (which I do own).  It might not be formal but it will be comfortable and shouldn't break the budget.  I can wear it to the holiday events coming up in December.  And I'll probably still get shoes.  According to What Not To Wear, my wearing of white sneakers to non-working out events is a fashion high crime.  As is most of the rest of my wardrobe, but until someone offers me a $5000 shopping spree, it's going to have to be baby steps.