Store pickup default location

[jbjconsulting]

When someone checks out an item I'd like it to either default to a particular pickup location or I'd like to limit the store pickup options to the location that is associated with that item.  For some reason I see all of my locations during checkout even though in the Edit Item screen I only have one location checked.  I'm guessing there's a way to do this, but I can't figure it out.