noob needing guidance.

I am very new to applescript and need some guidance on the best path forward. I am needing to create a GUI that will populate some type of drop down with a list of customers. Those customers each have their own folder in a specific location. then once a customer is selected I need to populate another drop down with he items inside that folder.

Again - I am a newbie and trying to get the right path. I have tried to research the NScombobox, but need some expert guidance.

Thanks in advance
tracy