script to change users' primary SMTP address

Hi,
i have csv file with list of 200 users name. all the 200 user's are having primary and secondary email ID. as per example :- 

user@smtp.co.in (as primary) and user@smtp.com (as secondary)

i need to change their secondary email address as primary and keep the old primary address as secondary.

Is there any Power Shell script for that? i am using exchange 2010 server.

Any help will be appreciated.

srini