Thanks for your reply. I have tried casting my custom typed object to a URLVariables object but that doesn't work.
Typically I am connecting to API's like amazon, google etc. using the WebService component in flex. Most of these api's require base credentials like a username, password etc. to be sent with every call. I was thinking of creating a base class called Credentials... Then creating new classes that extend the credentials class (replicating the api's request parameters for each method)... Then sending the extended class to the api method I want to call. Is there a better (or other) way to do this sort of thing? It doesn't seem practical to create a new object() and setup each property every time I want to make a call.