Invoke javascript from flash

To invoke a Javascript function from Flash use ExternalInterface.call()
http://www.adobe.com/devnet/flash/articles/external_interface.html#articlecontentAdobe_numberedheader_2 
http://livedocs.adobe.com/flash/9.0/ActionScriptLangRefV3/flash/external/ExternalInterface.html#call%28%29

To call the ActionScript method from Javascript use ExternalInterface.addCallback()
http://www.adobe.com/devnet/flash/articles/external_interface.html#articlecontentAdobe_numberedheader_3
http://livedocs.adobe.com/flash/9.0/ActionScriptLangRefV3/flash/external/ExternalInterface.html#addCallback%28%29

Example : http://jared.simplistika.com/as3-javascript-communication/