Calculate time difference between two orders per customer

I have a table like this:

Customer Order date
1 01/01/2013
1 01/21/2013
1 02/01/2013
2 01/13/2013
2 05/04/2013
3 06/13/2013

I need help to find out the time between first and second order of each customer - if the customer has more than 2 orders. I was thinking about using pivot table but was only able to find the first order time but not the time difference. Thanks!