Queries :: Query Records With Both Duplicate Values And Different Values?

I'm trying to determine the SQL to return only those records in a table which have duplicate values in each of two fields, but different values in a third field. Here's an example:

Code:

AcctNum FoodType FoodClass
------- -------- ---------
A123 Apple Fruit
A123 Apple Fruit
A123 Grape Fruit
A456 Potato Vegetable
A456 Potato Perishable
A789 Carrot Vegetable
A001 Banana Fruit

For the above table, I'm trying to return records which have multiple entries for AcctNum + FoodType, but DIFFERENT values for FoodClass. So for the above table, the query would return:

Code:

AcctNum FoodType FoodClass
------- -------- ---------
A456 Potato Vegetable
A456 Potato Perishable

It returns these two records because there is more than one record with for the AcctNum + FoodType (i.e. 'A456' + 'Potato'), but DIFFERENT values for FoodClass (i.e. one record has 'Vegetable' while the other has 'Perishable').