As Phil suggests I would try Standards Checker first. If that doesn't work for you then I would develop the vba as follows.
1. Start with the file to be checked open in MicroStation.
2. Attach the dgnlib/seed file to check against as reference attachment
3. Using the attachment.designfile object you can iterate through the levels and compare them to the activedesignfile
4. Detach the reference when your check is completed