Sql - updating multiple records with a sequential value

["Smith, Mike" <Mike_Smith@xxxxxxxxxxxxxxxx>]

I am adding some new fields to a file.  The file containts a master
contract#, contract# and (new) contract suffix

MASTER            CONTRACT      MASTER Flag		 SUFFIX
		  200300022                   Y		   00
200300022          200500120 		N
200300022          200500121 		N
200300022          200600124 		N

I want to be able to update the suffix with 01, 02, 03, etc for  each
master contract that matches a contract

So if mastflg = 'y', update suffix(incrementing value)  where contract =
master

Can I do this with SQL?    I'm not sure how to make the suffix field
increment. 

Thanks

Mike