Dynamic filtering of values in Input Control?

Hi,

Lets Say I have two fields in Input Control, Country with 20 distinct values and 600 associated Stores.Now If i select any one country in the input control, the input control for stores should only show associated value, not all the stores.

As it is impossible for the user to select from full list of 600 static list of values of store. Is there a work around to achieve this functionality?

Regards

Sushant