Attribute Updates after Save

Summary: We have created Product rules which update Item Physical Dimensions of weights by using following conditions

[Item].[Item Basic].[Organization Code] == "UK"

or [Item].[Item Basic].[Organization Code] == "GER"

Return= [Item].[CARTON DIMENSIONS & WEIGHTS].[MASTER CTN WEIGHT METRIC [KG\]] / [Item].[MARKETING].[STD SELL PACK], 5)

Condition works when we create and save Item but once we have saved Item if MASTER CTN WEIGHT METRIC [KG\} is updated then the value of Item Weight is not getting updated. Is there any way of adding condition that values are updated after save. Also of we have to run Analyze Item Rule Set Impact how can we schedule it that it only picks up new Item created that day not all