Dropdown list issue

Hi all,

I'm a newbie with Adobe LiveCycle Designer. So, please forgive me for my lack of knowledge about simple things.

I am about to finish creating a pdf file. I need to insert to dropdown lists: List A and List B.
The point is that I need them to work this way.

I.E. List A: a) Eurpoe, List B: UK, France, Germany
b) Asia, India, UAE, China
c) N. America USA, Canada, Mexico

If you choose any item from List A in List B should appear items with the names of locations from those areas accordingly.

Any ideas how to make it please.

Many thanks for your help.

Regards,
Ramunas