I don't know how much you know about LiveCycle so you may need some more information, and you are a bit light-on in what you are asking for but here are some thoughts...
Make your drop-down and add your choices and in the Binding tab click "Specify Item Values".
Make two-subforms, each containing a different design.
Use the Exit option on your Drop-Down to add an if (this.rawValue == 1) choose subform1. Enter another if statement for each of your drop-down options.
Good luck.