How can I do this? (youtube combobox)

Question

I am making a yt account creator in C# with webbrowser control.

but how can I choose "january" as birth month by clicking button1 in my application. what code should I write in button1 click event.

youtube register page:

http://anoney.com/?https://accounts.google.com/SignUp?followup=http%3A%2F%2Fwww.youtube.com%2Femail_confirm&continue=http%3A%2F%2Fwww.youtube.com%2Fsignin%3Faction_handle_signin%3Dtrue%26nomobiletemp%3D1%26feature%3Dheader%26next%3D%252F%26hl%3Den_US%26new%3Dtrue&ltmpl=sso&service=youtube&hl=en_US