Hi Ravi,
It is bit difficult (how ever if you have set up some triggers when ever the index is used),how ever we can use DMV to get some useful information -Last user -seek,scan,lookup,update via -sys.dm_db_index_usage_stats.
Check the link :http://blogs.msdn.com/b/sqlcat/archive/2006/02/13/531339.aspx.
Best Regards,
Rama Udaya.K