Left join in virtual cubes

Hello guys,
I have a situation that I could not solve and would like the opinion of you.


I have two cubes, as follows:

CUB_1
FACT_TABLE 1
DIM_1
DIM_2
MEASURE_1
MEASURE_2

CUB_2
FACT_TABLE 2
DIM_1
DIM_2
MEASURE_3
MEASURE_4

I built a virtual cube to integrate my two cubes, my two tables facts, and everything worked perfectly. My problem was when I include a new cub:

CUB_3
FACT_TABLE 3
DIM_1
DIM_3
MEASURE_5


When I filter by any attribute DIM_2 that exists in CUB_1 and CUB_2 are not presented metrics CUB_3, I think because there is no dim_2 in CUB_3.
I think a possible solution would be to use some type structure like LEFT JOIN, just do not know how to do this using the mondrian




Thank you in advance for help!