Q: Can I use an attribute for each menu item in the xml file to store some description about the menu item ? Then can I read it with Flash and display it into a dynamic text field ?

A: The drop down menu gives access to the currently selected menu item through the onPress and onRelease events. The event handler function get an Object parameter (evt) and evt.item is the reference to the actual selected item. Any attributes you add in the xml file, to each item's xml node, will be added as parameters of the item.

So when you need to have a description for each menu item just add the description attribute in the xml file and access it from the onPress or onRelease event handlers with evt.item.description. The same goes if you would like to have a parameter that contains the current position in a Flash site, when a menu item is selected. Just add the position attribute in the item's xml node, in the xml file, and reference it from the onPress or onRelease event handler with evt.item.position. What you do next with those values, it's up to you. You could put them into a dynamic text field to display the description text. The next example does just that.
Files: DDTM_CurrentSelection.zip