Check step C
Create a context mapping between the ...
Creating a context dependent code list.
Do you have field for Country or do you simply want to filter always by the same country?
Use the right-click option on data model field, as mentioned in the link above, and select the data type column to be filtered, and then the data field.
If you want to always filter by the same Country, define an unbound data field with the value hard coded in there.
Hope this helps.