markup - adding xaml code after render

I have markup view that displays data from different sources. I have data providers that makes xaml code for different containers which are then collected into one and xaml is rendered. The problem is that not all sources are ready at the same time. Lets say I have most of containers ready and I render Xaml which means it builds MarkupUI object etc. After some time other containers got it's data, made its xaml code and I want to display it as well.
Is there a possibility to add this code without rendering all xaml document from the begining?

BTW: is there a possibility to put an animation in the xaml (animated gif, avi, xaml animation)?

Thanks.
One more question about resources and it's styles. I have global styles in a page resources. Whould a xaml from container render properly if uses those global styles?
Probably i'll have to copy content of the global resources to a xaml element (StackPanel) i'm gonna render for container. Am I right?

ps. any plans for supporting animations? :)