Call Grade DFF while validating values at assignment level

Summary:

i am trying to made validation on Promotion transaction using the Old Grade and New Grade values but i am not comparing grade to grade simply i need to compare dff maintained at Grade level to make the validation

Content (required):

While promotion of an employee , if grade changed i need to compare dff with serial number maintained at grade screen to double check that HR specialist does not choose lower grade by mistake

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

22b

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