Just use a cursor for that. Details including example can be found in Books Online.
HOWEVER! Why do you need to do this? There is almost certainly a better way to handle your problem than looping through all rows in a table. Please provide some details as to why you think you need to loop through every row.
The RIGHT answer is NEVER use a cursor. SQL words with entire sets of data at one time, not like mag tapes and record at time processing. You need to study RDBMS for about a year before you post again.
--CELKO-- Books in Celko Series for Morgan-Kaufmann Publishing Analytics and OLAP in SQL Data and Databases: Concepts in Practice Data, Measurements and Standards in SQL SQL for Smarties SQL Programming Style SQL Puzzles and Answers Thinking in Sets Trees and Hierarchies in SQL