taxonomy relation question

Hi,
First of all thanks for this nice plugin.

I have one question about the taxonomy relations. Is there a way that I can bring only the parent taxonomy for one field and then based on the selection of this files show the children in another?

For example I have a field named country which I use to show the taxonomy location. I would like this field to show only the parent parent terms in this taxonomy(united states, United Kingdom etc.., for example).

Then in another field which I will name state I would like to show the children of selection in the previous field country.

Can someone guide me or point me in the right direction here?

Thanks in advance!

Hope someone can help! ??