Hi, not sure if I understand you correctly, please correct me if I am wrong. Based on my understanding, you have two fields which are Country and Direction, Country field contains values like "Indonesia","Singapore","Malaysia"...etc where Direction field contains values like "North","South","East","West". Now, you want to have one selection box which is only one listbox to have selections like "North Indonesia","West Indonesia","South Indonesia","East Singapore"...etc and then you want your table to show the Country Region according to user's selection.
In order to achieve that, you can use expression: Direction&' '&Country as your listbox expression and your table dimension.