Setting the textfield of a Flash form (Webbrowser)

I'm trying to fill in the username & password using the Webbrowser control on a page containing flash for the login input. Specifically, the page I'm trying to work with is https://www.siriusxm.com/player/ and since the element ID is embedded into the flash itself, I've been playing around with SetAttribute. Having no success yet, I'm starting to think my efforts are futile.

Right now I'm using a series of SendKeys code using {TAB} and such, even though it seems pretty stable, it's just not the route I want to go.

Hopefully someone can point me in the right direction, if it's at all possible.

Thanks.