Hi Rohit,
I think that all the columns will be displayed. You cannot choose the columns that has to be displayed.
Instead of it, you can assign a search help to that field. You can choose the exporting parameters which in turn displays only the columns specified.
Since you have to display fields of 2 tables, your selection method in search help should be a database view.
Create a database view and appropriate conditions for this view.
Please refer this thread:
http://scn.sap.com/thread/3147015
Hope, this helps.
Thanks & Regards,
T. Prasanna Kumar