We have hierarchy type lists of Market Unit and Country Group (Market Unit is parent.) and Country Group list is specified as a dimension of a module. In the module, the line item 'B' is applied to Market Unit.('Applies to' of the line item 'A' is left default.)
In such a situation, if user selects one of the Country Group in the Page selector in the module, the line item 'A' only needs to be shown ('B' should be hidden.) When one of the Market Unit is selected, 'B' only needs to be.
Thank you for your helpful advice and screenshots attached.
However, 'Applies to' column in blueprint of the line item 'B' is set to 'Market Unit'. On the other hand, one of 'A' is 'Country_Gourp' (left defalut). So IF formula you mentioned cannot be put because dimensions of 'A' and 'B' are different. Error message has been shown as the attached screenshot.
Good point. In this case I would suggest creating a new line item (ex. Line Item B Drill Down) to bring line item B down to the default Applies to. Hope this will not significantly influence your model size.
The screenshots of the solution are in attachment. Note that Summary should be Max or Min or Average for "Line Item B Drill Down" and Formula for "Value to show".