Hi Anand,
We had delivered similar kind of functionality to one of our client. We disabled the export functionality from OWL screen - Lead, Opportunity, Accounts, Materials, etc..
If you need any assistance on this, kindly contact us.
Regards,
Navabarathi M
ERP LOGIC INDIA Pvt.Ltd
Cell : +91 850 875 1800
E-mail - navabarathi.mohanraj@erplogic.net