So.... To make sure I understand you correctly... Your description is build up from the content of the "primary", "secondary", "tertiary", and "fourth" boxes.
You want the user to be able to pick "01 CONNECTOR ASSEMBLY" for primary, then maybe "23 PLASTIC" for secondary, then maybe "02 FOUR PIN" for tertiary, etc.
Then, you want the description shown on the drawing to be "CONNECTOR ASSEMBLY, PLASTIC, FOUR PIN" automatically.
If this is the case, you could use VBA in an equation to ignore/concatenate to build your description automatically based on the four custom properties that contain the number/word combinations.
You hit the haed of the nail-
I however, am not familiar with VBA or scripting.
I will see if anyone in the office can help with coding.