FAPI #states for multiple selections.
You should be able to define something like this:

'visible' =&gt; array(
  array(
    ':input[name="ELEMENTNAME"]' =&gt; array(
      array("value" =&gt; 'VALUE_1'),
      array("value" =&gt; 'VALUE_2'),
    ),
  ),
),


See this question  for more details