Here is a code fragment from WebStore feature that shows how to add extra links into the breadcrumb links, this one adds 2 links.
Control c = Master.FindControl("Breadcrumbs");
if (c != null)
{
BreadcrumbsControl crumbs = (BreadcrumbsControl)c;
crumbs.ForceShowBreadcrumbs = true;
crumbs.AddedCrumbs = "<a href='"
+ SiteRoot + "/WebStore/AdminDashboard.aspx?pageid=" + pageId.ToInvariantString() + "&mid=" + moduleId.ToInvariantString()
+ "'>" + WebStoreResources.StoreManagerLink
+ "</a> > <a href='"
+ SiteRoot + "/WebStore/AdminDiscounts.aspx?pageid=" + pageId.ToInvariantString() + "&mid=" + moduleId.ToInvariantString()
+ "'>" + WebStoreResources.DiscountAdministration
+ "</a>";
}
Hope it helps,
Joe