Sql-server – Need to filter dimension where two attributes are the same

I've obfuscated the scenario but the general idea still applies, so if the schema seems retarded, it probably is in this example…

Let's say I have a Student dimension, and in it are two attributes – Major and Minor (subjects).

I want to be able to create a Named Set in SSAS that gives me Students who have somehow been recorded as having the same subject for Major and Minor…

Dimension looks a little like this:

Student
  - Major
  - Minor

The underlying table looks something like this:

StudentID  |  MajorKey  | MinorKey
1             50          51
2             45          101
3             58          56
4             45          45

So, in effect, I want an MDX expression like this:

FILTER (
  [Student].allmembers,
  [Student].[Major] = [Student].[Minor]
)

… but I can't quite figure out the syntax. Any ideas?

UPDATE:

If I use this syntax…

FILTER (
  [Student].allmembers,
  [Student].[Major].Properties("Key") = [Student].[Minor].Properties("Key")
)

Then it slows down the ENTIRE cube for some reason. Every Measure (natural or calculated) takes several minutes as opposed to 1-2 seconds pre-cache.