If you are away for that long, I hope you have already arranged for the PO to hold your mail until you return. There is a charge for this and well worth it. Do it today, it takes a couple of days to kick in. Most Chinese, Canadian and American sellers use the postal system.
If the seller used the Global Shipping Program, you can't.
If instead of the PO, the GSP is using CanPar, and there is no way of knowing. You could try phoning CanPar and explaining the situation. However, they are geared up for business, not personal, delivery and may not be able to catch your parcel.
