update status and progress bar on popup from VM

I have a simple UserControl that has a textblock and a progress bar.  The textblock and bar are bound to some values in the ViewModel.

I have defined this control as a popup like this.

<Popup IsOpen="{Binding Path=ProgressShowing}" AllowsTransparency="True"
                   HorizontalOffset="0" VerticalOffset="0"
                   Placement="Center" PopupAnimation="Fade"
                   Width="385" Height="115"><popControl:PaymentFinishProgressView /></Popup>

My idea is to trigger the ProgressShowing to pop this little dialog up and then update the status and progress bar from the VM, while it is busy working on something. 

Problem is when I update things, I don't see anything.  Then the last second I see the popup flash on the screen and its gone.  I was thinking I need to either force a refresh or take a different route all together. I would prefer the former to the later as this is a very easy approach.  I am not sure how to use InteractionRequest to do something like this.

Thanks for your time.