Hi,
I am not exactly sure how your configuration should look like.
If you need to run multiple sites in one installation you could follow instruction described in
Configuring multiple websites article.
Another possibility is to configure
Nested web sites.
You can set 2 sites in IIS, both pointing to the one project folder.
But I think that you are looking for setting, where there would be 3 sites in IIS, 3 partial project folders and everything would be managed from one place. Unfortunately, this is not possible.
Best regards,
Ivana Tomanickova