FMPA 11 on OS X 10.6.8

Say I've got two tables X and Y.
Table X has four fields: Dog Breeds, Cat Breeds, Horse Breeds, and a global Animal.
Table Y has two fields: Animal and Breed.
I create a relationship from X::Animal to Y::Animal.
Then I create a value list using values from table Y's Breed field, including only related items starting from X.

If I've done this correctly, I should end up with a conditional value list that depends on what's entered in the global Animal field. If the field contains "Dog," I should get a value list of only dog breeds and so on.

Now if I attach an OnObjectEnter script trigger to each of table X's breed fields to set the global Animal field, shouldn't I be able to see a drop-down list of the just the corresponding breeds when I click into each respective field?

I must be doing something wrong because when I click into a breed field in table X, I get a blank drop-down list, even when I can see the global contains the correct animal for the relationship to work.

Help, please.

Andre