Hi,
I believe you could benefit of the IModuleCatalog implementation provided with Prism. As you may find the ModuleCatalog holds information about the modules that can be used by the application. This way in its Modules property you could find a collection of the ModuleInfo classes. This ModuleInfo classes will contain information of each module like the ModuleName and the ModuleState, which for example you could check to see if a module is "NotStarted" and react accordingly.
I hope you find this useful,
Agustin Adami
http://blogs.southworks.net/aadami,