How to check if a document is classified or not during promotion event?

Requirement is to perform validations on document promotion.This is to allow user to promote or block based on validations.

List of validation:

  1. Check if classification is connected
  2. Check if few attributes are filled in or not

EKL :

I was able to perform checks for attribute and child relations under Document with "ER generic server openings"opening ID.this is done on pre-commit promote event.

But I am not able to check if the document is connected to classification or not because Classification is on from side(parent).

 

Maturity Graph :

No predefined control rules for this scenario.

 

Is ther  a different way to achieve this?

 

Note: customer is not using change process