Parameter Query - Using Choose Function

I need to allow a user to select criteria as part of a query.

Running the query manually I would type in either:

"Core Stock"
OR
<>"Core Stock"

in the criteria field of the column.

I tried using the following parameter in the design grid:

Choose([Select 1: Core Stock 2: Not Core Stock : ],"Core Stock",<>"Core Stock")

The "Core Stock" option works but the <>"Core Stock" returns no records.

I would prefer not to use a form if possible . Any ideas ?
Regards

David