MDX Expressions

[Database Administrator]

I have the following three related tables.

Trap Table Marks Table PIC_FishMarks Table

FishID (PK) ID (PK) MarkID (PK)
.. FishID (FK) Acronym
.. MarkID (FK) Description
..
Count

I have created a snowflake dimension called marks usin Description from
PIC_FishMarks, which relates back to Trap Table through Marks Table by the
Foreign keys listed above.

Trap Table contains 10,000 records and Marks Table contains 100 records, I
want to create an MDX value that says, if a FishID from the trap Table is not
in the Marks Table the a record should be added to the total count with a
description of "No Marks".

Is this possible, Please let me know if you need additional information and
thanks for your help in advance.