Workflow - email needs to show old material description.

Experts:

I am trying to show the old material description in a workflow email and am having difficulty with the coding.

When the material description is changed, the email is triggered and I have it showing the new material description.  I know that the old material description field that I have defined in the business object needs to be defined as virtual.  And I am trying to determine how to code things in order to extract the old value from the table CDPOS but am having problems.  Is anyone able to provide some coding guidelines that I can utilize in the business object?  Coding examples of how to extract CDHDR to get the document ID and then CDPOS to extract the old field value would be appreciated.

Thanks for your time.

Chris(tine)