SSAS : Field (Y/N) 'a' in Fact A impacts on rows Fact B

I've a requirement from a customer about combining facts and selecting them with a Y/N field. This blogpost descibes this requirement and the translation in a solution. This blogpost is simplified version of the 'real world' situation. Suppose you have two facts : 'A' and 'B'. Fact A has a field 'a' and this field can be Yes or No. The user wants to use this field to limit the rows in Fact B, somehow.