Hi,
My suggestion follows
- Try to check any appropriate change document object in SWEC transaction,if you found it will be very easy add up event here.Refer following link
http://scn.sap.com/docs/DOC-44084
2.If you couldn't find Change document make it simple find the save exit for your transaction,While changing just trigger the event by using "SAP_WAPI_CREATE_EVENT" FM.(Here before raising event you can do Status check or some other filed check like validations also)
If you have any queries,Let me know.
Regards,
Ragav