Actually what data u want to export to excel?
You can pass the data to java Using HttpService or by Using DataServices and from there export Data to Excel.
If you know how to call a Java method from Flex (for example using Blaze Data Services) you could use Apache POI library for that one. It should be working well, I've tested it many times.
I agree with cemef. You can use Jasper & Ireport to do this too. I think that is easier that just POI (jasper & ireport there's POI with dependency)
Need to export into MS Word not in Excel
I need to export Flex data (Graphs, charts) into Ms Word document ( Whatever data is visible on the Screen).
the point the others were getting at is that yuo need server-side capability to do this, whether Excel or Word. All Office products have an extensive API surfaced via ActiveX but Flex cannot talk directly with this. You need to pass back to the server whatever parts of the user selection you want and then run a process on the server to do any transfer into Word.
Your other option would be to use the clipboard - in Flex 3 you do not have access to this, but in AIR, or in Flex 4 your options are more extensive.
If is Word or Excel its doesn't matter, you'll still need jasper and ireport on your server. I confess that is a little difficult to use text with charts inside. In this case you'll need another API called JFreeChart that can be use with jasper. Take a look in google that you'll see a lot of samples using these APIs.