What are you trying to do, and what is the result (error, warning)?
Most events are dispatched automatically by Flex, like when you click a button MouseEvent, or get a result back from HTTPService ResultEvent.
You sometimes need to dispatch events manually, but that is more rare. If you have custom events, you will need to dispatch events.
See these links:
If this post answers your question or helps, please mark it as such.
Greg Lafrance - Flex 2 and 3 ACE certified
Flex / AIR Development, Training, and Support Services