Deleting shared cells in a Microstation File

When I try to delete a level, the Message Center is stating that the level is being used. How can I determine where the level is being used at?

You can use the key-in: LEVEL USAGE . Where you substitute for the name of the level that you are trying to gather information on. In some cases, the levels may be used by Shared Cell Definitions. You can remove the shared cell definitions from a design file by using the key-in: DELETE SCDEFS ALL.