RadBusyIndicator A web call and a DispatcherTimer locking my UI. Need cancel button Windows phone

RadBusyIndicator A web call and a DispatcherTimer locking my UI. Need
cancel button Windows phone

So here's the setup.
on button click
private void login_Click(object sender, RoutedEventArgs e)
I make a webcall
classes.WebDataAccess.Login(uname.Text, pword.Password);
Then start a DispatcherTimer
timer.Interval = new TimeSpan(100);
timer.Start();
Which it then checks if the web call returned anything on its tick
void timer_Tick(object sender, EventArgs e)
{
if (classes.WebDataAccess.LoginBag.propBag.Count > 1)
{
...
This all works swimmingly. EXCEPT stupid Windows Phone certification
requires you to have a cancel button. So I added a cancel button and the
UI is locked... You cant click it.
I have tried putting all of this inside a delegate
I have tried putting it all inside a Dispatch.BeginInvoke thread
I tried putting async on the tick method.
I even tried getting rid of my rad control!
Nada, nothing... For some reason the UI is locked.
I need a quick fix