Hi Dan and welcome to the forum! Oxycodone is a short enough acting opiate that you may be OK to take some sub at 8:30am on Monday. The trick is to start with a very small dose like 1 or 2 mg. If that doesn't throw you into withdrawals after a couple of hours, go ahead and take another small dose.
What is your daily dose supposed to be? If you are thinking that you will be taking a total of 2mg/day, then just take smaller trial portions in the morning. I'm thinking that you are not under a doctor's care or the doctor would have given you this information? If you don't have a sub doctor now, I would try to find one if I were you. It's a lot easier when you know where your sub dosage is coming from.