I have a feature layers with states and counties fields. I want to make a selection tool. Tool dialog should have input for feature layer and two drop downboxes for states and counties. When user gives input feature layer, states drop downbox should get updated with unique values fron states column so that user can select state. And when user select state the counties dropdown box should get updated with the counties of the selected state, so user can select county from the selected state only. After that when user click on ok button the respective county should get selected on map. Can anyone please tell me how can I achieve this using model builder or python script in arcgis desktop?
I think you should be able to do this by customizing your tool dialog's behaviour.
The relevant pages of the Online Help can be accessed via this one.