MEF : Use Export and Import from other project - silverlight-4.0

Question

I am using MEF in my silverlight project to download Xap file of other project on a button click.
But I have to give reference of that project in my current project and after that when I run my project it includes dll file of my other project in my current xap file and then I can use export and import of other project in my current project.
But I dont want dll of other project in my curent xap file and when I click ok button then after I want to download xap file of other and want to use Import and export without giving reference of other project.
I can download other project's xap file on button click event but i can not use Export and Import which i did in other project if I did not give reference.
Without giving reference can I use import and export of other project?
If yes then how can I do this?
I used below code to download xap file of other project it works
PackageCatalog cat = new PackageCatalog();
var catalog = new PackageCatalog();
catalog.AddPackage(Package.Current);
Package.DownloadPackageAsync(new Uri("Test.xap", UriKind.Relative),
(args, p) => cat.AddPackage(p));
var container = new CompositionContainer(catalog);
container.ComposeParts(this);
}
Thanks,
HItesh