CSS Commands From Flash?

I’m working with a developer who has set up a simple scheme where the video on a page moves itself to the center of the page upon a click of a button. The button needs to be in Flash.

Question is: how do you call a CSS command (which I know nothing about) from inside Flash?

We need two flash buttons to call the following commands:

onclick=“document.getElementById(‘contentBox’).style.display=‘block’”
onclick=“document.getElementById(‘contentBox’).style.display=‘none’”

Suggestions would be very much appreciated!