Enable disable jQuery Tabs

I have  JQuery Tabs on my aspx page with 2 Tabs ..Tab 1 - Sign in  and Tab 2 -  Confirm Order

  i want is to enable Tab 2,,  only  if the User successfully login  himself in form of Tab 1

Tab 1 has two textboxes( username and password) and One submit button in it for login ..

other wise the link of Tab2 remain disable i.e; on click of tabs it doesnot open ,and click color remains fade

i am using Jquery UI for tabs..