Refresh data in page of TabbedPage when viewed

I currently have a tabbed page, set up like:

public class SponsorPage : TabbedPage
{
     public SponsorPage()
     {
         this.Children.Add(new NavigationPage(ViewFactory.CreatePage(typeof(CaptureLeadsViewModel))));
         this.Children.Add(new NavigationPage(ViewFactory.CreatePage(typeof(PreviousLeadsViewModel))));
     }
}

The second of the two contains a dynamically loaded list view. From what I've been able to accomplish, these two views are both instantiated when SponsorPage is instantiated. That means that all of the data for the PreviousLeadsPage loads one time, and if they click between the two tabs, that data remains the same.

How can I do something, for example, PreviousLeadsViewModel.GetPreviousLeads() everytime the second tab is loaded?

Thanks,
Tom