How to script enabling screen sharing

Question

I'm trying to find an easy way for a non technical user to allow me (a technical person) to access their screen remotely over the internet.

(I'm tunneling via SSH so they don't need to open their vnc port in their firewall.)

I'd like to write a script that:

• Enables sharing.
• enables screen sharing
• sets "new connections must ask for access"

I would also like to be able to disable sharing too.

How could I do this?