Contextual Navigation

I’m trying to make a site with wordpress and not just a blog. I’m wondering if anyone can point in the direction to make a contextual navigation.

I have a bunch of static pages

Main page 1
|_sub page 1
|_sub page 2
Main page 2
|_sub page 3

Where I want Main page 1, Main page 2 to be tabs, then clicking on Main page 1 tab goes to the page but shows this navigation on the left column.

Main page 1
|_sub page 1
|_sub page 2

Any idea how this can be achieved? Is there a plugin?

Thanks