How to schedule jobs in Sql server 2008 for less than 10 sec?
Create a job that is scheduled to start every minute.  Have the job do something like:

WHILE 1=1
BEGIN
    EXEC dbo.SomeProcedure; /*  this would be the 
        name of a stored procedure that does the 
        actual work */
    WAITFOR DELAY '00:00:03.000';
END