I'm still a little unsure on what it is you're trying to get at, but you may want to look research Quirky Updates.

A word of caution: please note that this is an undocumented feature of SQL Server. When properly implemented it will reliably work, but if you are not familiar with what they do or the nuances of them, I strongly suggest you read up on how they work. Jeff Moden has a great post about how they work.

http://www.sqlservercentral.com/articles/T-SQL/68467/

Often a properly written quirky update will be the fastest way to serially move through a table, modifying values on one row and then using them on the next.