Circular dependencies between modules

Circular references between modules, constants, and user-defined types aren't allowed. This error has the following cause and solution:

• A user-defined type or constant in one module references a user-defined type or constant in a second module, which in turn references another user-defined type or constant in the first module.

  Remove the dependent references.

For additional information, select the item in question and press F1 (in Windows) or HELP (on the Macintosh).