edit the sidebar

Good afternoon.

I am new to wordpress so I am sorry if this is a stupid question :p

I am setting up a webpage with only static pages. I want to do it in wordpress to make the editing easier for a friend of mine.

In the topmenu a tab is created for the pages that I create, thats all good. Now i would like to make the menu in the sidebar dependant on the top menu.

When I click a link on the topmenu, i want to show subpages for this page in the sidemenu. Is there a good plugin for this or do I need to edit the code manually?

Thanks in advance!