Department Name validation based on legal employer name

Summary: Hello, we want to create an autocomplete rule where department name is validated based on the employee's current legal employer. For eg: if Legal employer is United States, then department name should begin with 5011, if Legal Employer is India, then department name should begin with 3011 and so on. Can anybody help with this requirement?

Content (required): Department Name validation based on legal employer name

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):