multiple list selections

multiple list selections

  
Hi,

I'm developing an application that lists different Governorates and districts. I did the following:
1-I created an entity (Normal one) and bootstrapped its values from an excel file i have with 2 attributes; One governorates and one for correponding Districts...Gov. records are duplicated while districts are unique.
2-I used Combo boxes to get list values from the Governorate atttribute, but unfortunately its duplicated.(Need to be resolved).
3- i believe i shall create screen action to excute aggregate to filter the entity based on selected value in Gov. combo box and populate the result in thew second combo box that i need to create for districts.

The Question : is there any other solution; if no, how i can solve the duplication issue in point number 2 ?