Hello Harish,
First, thanks for your response. I did some digging on AET and found these links:
http://scn.sap.com/thread/3177669
http://scn.sap.com/thread/3252309
In these links I've got some insight about the matter, but I still have some issues understanding this.
The three links presents the solution for adding a new field for a search screen creating it using EEWB or EAT. Either solution will create the field, but I still can't understand how I link this field with search criteria for it to know how to validate both the Complaint and the Tasks of that Complaint and filter by the Task (new field added on the search screen).
Thanks in advance,
-h