Update Null value based on next record value

Hi,

I have a Table as 

DateName InvNo
10/05/2012aaaaNULL
10/05/2012aaaa111
10/05/2012aaaa111
10/05/2012bbbNULL
10/05/2012bbb456
10/05/2012bbb456

I want to update Null invno values with same name/date values INVNO from next records.

Virendra Yaduvanshi http://wikidba.wordpress.com/