Dynamic select options in form

[g.fitini]

Hi to every one, i want toknow if it’s possible to do something like that.

For Example, i’ve a a field like : 


<field name="idState" title="state" field-name="state" 
          <drop-down allow-empty="true" current-description="">
              <entity-options description="${idState}" key-field-name="idState" 
entity-name="TableStates">
                  <entity-order-by field-name="idState"/>
              </entity-options>
          </drop-down>
      </field>

So, i can do a choice, between : {U.S.A., Europe, ...etc}

Now in the same form, i want another dinamic field where, i can choose just the 
Country associated to the field named ‘idState’.


<field name="idCountry" title="Country" field-name="Country" 
          <drop-down allow-empty="true" current-description="">
              <entity-options description="${idCountry}" 
key-field-name="idState" entity-name="TableCountry">
                  <entity-order-by field-name="idCountry"/>
              </entity-options>
          </drop-down>
      </field>

So, if i’ve choice  ‘Europe’  in the field ‘idState’, i want that appear in the 
field ‘idCountry’ a select with : {Italy, Spain, Greece,...etc}

States, and Countries, are in two differents tables. And the countries has a 
reference to States table.


Thanks in advance.