Displaying Loading image during loading in Asp.Net(C#)

Hello,I am using Visual Studio 2008 .
I  went through one problem,Actually I have one page suppose default.aspx,In that page I have 4 IFrames,
in each IFrame there is one .aspx page,my question is that When I go to default.aspx page,then before loading
the data of each frame individually(because in each frame it takes a time to load data)I want to show one flash image(.swf),
as data of particular frame is loaded that image  should be gone for that IFrame(whose data is loaded sucessfully).That means before loading of complete data that image should display and as data is loaded,image should be gone.
  Is there any way to acheive it,I will be thank full if i will get my solution.

Thanks