Thanks for the suggestion . Unfortunately this doesn't get what I am looking for What I really need is, once the user make selection in MAX_Days, the expression calculates the TOT_VOL all the TEST_CODEs that has the selected MAX_days.
ex. if I select 5, it will limit to REF 2 and 4 in TABLE 2 ( blue color). Where as I want to find the SUM(TOT_VOL) for all B&D TEST_CODES ( Blue and Red)