Add reference always picks a certain file, even if I add a local assembly file

Question

I have installed blend which installs Microsoft.Expression.Interactions.dll which I reference in my project.

If I copy this dll to a folder local to my solution and reference that copy, when I look at the properties of the reference in visual studio it always shows the path to the version that blend installed.

It only changes to the local solution path if I rename the folder that blend installed so it can't find the original version. (I just did this to see what would happen)

Why does it do this? Is there a way I can force the reference to use the local file as it's path and keep the blend assemblies in their original place as well?

Thanks!