Hello Anita,
You can find the answers to your questions in the "The Book Of Beta Sigma Phi", which you should have received when you received your pledge ritual. If you do not have one, you can purchase one from the Beta Sigma Phi Gift Shop, their ph # is 800-821-3989.
According to this book you should allow approx 30-45 min for the business meeting and 30-45 minutes for the program; however, I have read somewhere else (and I dont know where) that the program should only be 15-30 minutes. I think it is just up to the chapter.
As far as dress is concerned (we are a career chapter and are more relaxed in our rules) but I believe the only time that you are required to "dress up" is during rituals, installation of officers, founder's day and when ever your chapter has a special occasion.
Again, this is up to the chapter. Some chapters have formal dress for rituals, others wear "church" clothes, while others don't dress up at all.
I hope that this info has helped you.