question of BgImage

When my setup is installing files,how to do that another window is playing background pictures to synchronize the installing process?

Please give me a detail solution!

Thanks for help!

The bundled BgImage example that comes with NSIS didn't help?
CF

I implemented that with the following way,I think it's a blunt solution.I hope someone can give me a good way!
***********************************************************
I divided my files to some groups:file1,file2..file'n
Function .onGUIInit
...
FunctionEnd
Section bg
File file1
...;Insert a bgImage here
File file2
...;Insert a bgImage here
File file3
...;Insert a bgImage here
....
SectionEnd