Business Rule formula to check if documents added before completion

I have set up a basic formula to check if a document has been added to a task before the task is completed.   There are basically 2 pieces that would trigger the business rule error, if no document is added and if the after state value of the task status is complete (CPL or CPL:A).     

What works:    When I attempt to complete a task using the Percent Complete slider to 100% or change the status drop down to "Complete", I receive the error as expected - fantastic!

What is not working:   If I close a task through the "Mark as Done" option in a task, the formula does not appear to recognize the change and does not flag the error.   When i ran a Journal Report, it appears that a task that is closed via the Mark as Done button goes through a "DN" status and then moves into a "CPL" status.   I have attempted to account for this in the formula but still does not seem to catch a task from being marked as done without a task.  

Any ideas? 

Formula:  

IF(

     {hasDocuments}=false && 

    (CONTAINS("CPL", $$AFTER_STATE.{status}) || CONTAINS("DN", $$AFTER_STATE.{progressStatus})),

        "**** Warning! **** You cannot set this task to complete until a document is attached"

  )

 

 

Sample Images: 

 

Closed via Status drop down or Percent Complete Slider - works as expected

 

Closed via Mark as Done and the task closing without document (error we are attempting to prevent)