If you are a windows mobile phone user, maybe I can help you. Recently, I have searched a kind of new software named Pocket Call Blocker. It is designed for windows mobile to block unwanted calls and sms.
If you have interests in it you can have a look at : http://www.pocketcallblocker.com/how-to-block-unwanted-incoming-calls-on-windows-mobile.ht ml
Hope help ~~
your question is not very clear but if i understand you correctly you want your methods to be thread safe?
Flex is single threaded and so you do not run into these problems