[AOII Angel]

You might want to call the greek advisor and ask if you can write a letter to the sororities whose parties you'll miss tonight. Towson allows this, and I've heard many a letter during member selection sessions from PNMs who could not attend a party for one reason on another. This would allow you to give out the information that you didn't give them earlier, ie. you are really interested in their chapter but couldn't miss your biology lab. It may not make a difference, but at least you let them know that you liked them. I personally think this is a fair option since the rest of the PNMs are allowed to tell the chapters this in person.