How can I validate the structure of XML documents I am editing?

I understand that IDEA does some basic validation, i.e, placing the cursor at the end of a mismatched tag will change the background of the brackets to red.

What I want to do is hit a button (or better yet real time) and have the entire structure be validated. I am not concerned with DTD or Schema validation.

The ultimate would be to have the little red lines appear where the structure is not valid.

Thanks.