Write an OnNewDimensions event handler to respond to changes that alter the data array, such as when the active property of a dimension in the data cube changes. When OnNewDimensions occurs, the information the decision source can provide changes. To respond to changes that reorganize the data but do not change the data cached by the data cube, use the OnEndPivot or OnLayoutChange event. To respond to changes in the data cube itself, use the OnStateChange event. 

OnAfterPivot 

OnLayoutChange 

OnStateChange 

OnSummaryChange 

Using Decision Sources