Position relative to a sidebar

[CodyBontecou]

I'd like to create an effect similar to Google Maps, where the minimap moves relative to the detail drawer.

i.e. When the drawer is closed, the minimap has a 5px margin from the edge of the screen.
When the drawer is open, the minimap has a 5px margin from the edge of the drawer.

As you can see in the second picture, the minimap maintains it's position regardless of what I create. I'd like to gain some control of this behavior if possible.