Thank you for reaching out.
I understand you wish to set your Virtual Hub to prefer VPN routes over Express Route.
Have you tried setting the virtual hub routing preference configuration to VPN instead?
You can change this configuration as documented here
Just as FYI When a virtual hub has multiple routes to a destination prefix for on-premises, the best route or routes are selected in the order of preference as follows:
- Select routes with Longest Prefix Match (LPM).
- Prefer static routes learned from the virtual hub route table over BGP routes.
- Select best path based on the virtual hub routing preference configuration.
If your VPN routes are more specific those will be selected. Thanks