How To Create Stored Procedure Change Value Once A Month From 1,2,3,4 TO 2,3,4,1

help
i need to create stored procedures that run once month
change value (UPDATE) once a month in one table the values from 1,2,3,4 next month 2,3,4,1 ..... 3,4,2,1 .......4,1,2,3 ..... 1,2,3,4
i have this code



Code Snippet
SELECT empID, location, ISNULL(NULLIF (( location + DATEDIFF(mm, location_date, GETDATE())) % 4, 0), 4) AS new_location
FROM dbo.empList

like this the employee go from one location once amonth to new location






table on this month (5)
empid location location_date
--------------------------------------------------------------

1111 1
222 2
333 3
444 4

5555 3
666 2
777 3
888 4

table on next month (6) (after a month)
empid location location_date
-------------------------------------------------------------------

1111 2
222 3
333 4
444 1

5555 4
666 3
777 4
888 1


TNX