The SelectionTree control uses the SelectionSize event to publish the size of the highlighted item. If it is a parent item, then the number of children selected is also published. The string is one of the SelChildCostPos, SelChildCostNeg, SelParentCostPosPos, SelParentCostPosNeg, SelParentCostNegPos or SelParentCostNegNeg strings from the UIText table. This event should be authored in the EventMapping table.
This event can only affect controls that are located on the same dialog box as the SelectionTree control.