Yes, when you make your offer on a home there is a field in the PA agreement of sale that you need to fill it that says the low and high interest rate you will agree to. So, If for some reason before the seller signs your offer and excepts it...and the interest rates go up then you do not have to purchase the home. Soon as the seller signs your offer....you mortgage company should lock your rate so then you do not need to worry about the interest rate moving from the time that your agreement gets accepted from the seller and the time that you go to settlement.
I hope this helps. I have other Home Buying Tips for PA buyers at my website...I do not cover your area but my video's cover all of PA.