Use a sp_WhoIsActive with the @delta_interval option:

http://sqlblog.com/blogs/adam_machanic/archive/2011/04/26/delta-force-a-month-of-activity-monitoring-part-26-of-30.aspx

and you can also save the results in a table, but the @delta_interval option should be enough for you:

http://sqlblog.com/blogs/adam_machanic/archive/2011/04/25/capturing-the-output-a-month-of-activity-monitoring-part-25-of-30.aspx