I have been trying to work out how to make rule driven links between two cubes work properly today. One key thing that I have learnt from the Guru is to have separate elements in my Measures dimension for each source cube. This is to avoid the situation where links from multiple cubes overlap the result in the target cube.
For example, I have a GP cube, an Opex cube and a Factory cube. Guru’s recommendation was to have separate elements for each source that roll up to a common parent. So in this example, having Amount – Opex, Amount GP and Amount – Factory all rolling up to Amount, means that each source cube has its own target measure and they then all rollup.
Also note that this solution was only recommended because there is no data entry into the target cube.