Visual Studio Setup and Deployment - Installation Folder Selection

I have a VS2005 Setup & Deployment project and I've run into an issue that I would like assistance with.

Here is my issue:

The 'DefaultLocation' for my application is set to '[ProgramFiles开发者_如何学CFolder]\MyApp'. Now I would like the user to select what drive to install this application to. I know this is accomplished through the 'Installation Folder Selection' dialog, but I want the user to be able to select a drive only, not the entire path.

My question is how do I capture what drive the user selected from the 'Installation Folder Selection' dialog and use that drive letter to tack on to my 'DefaultLocation' variable?

Example: If the user selected "M:\" from the installation folder selection dialog, I want to install to "M:\Program Files\MyApp" or if the user selected "E:\", then install to "E:\Program Files\MyApp".