Exposing custom field and custom option group to advanced search export

Question

I have a custom field (tempField) and a custom option group (tempGroup) with options (1, 2 and 3)

I want to expose these to the export form. For example, when you choose "Individual -> Phone" field in the advanced search -> Export screen, you are presented with two child select fields (location type and Phone type).

I've set "export" key to "true" in my DAO so the field is appearing on the export form but after selecting the tempField, the tempGroup option list doesnt appear.

Is there a way to achieve that ?

Thanks in advance.