Hi..
you can work with your abap-er (unless you are fluent in abap yourself) and create a validation in wbs level that will use function module STATUS_TEXT_EDIT 2 times (one with parameter BYPASS_BUFFER = '' and also BYPASS_BUFFER = 'X' to check if the status actually changed from CRTD to EXEC. In one case the function modulereturns the status that was saved in database and in the other case it reads the status from the buffer in case the user has changed it and has not saved the results yet).
If this is the case you can check on COBRA/B tables if settlement rule exists and pop-up error messages.
Let me know if it works
Panagiotis