Hi,

I'm not going to write this for you but i'm pointing you!
RsForms isn't able to solve this, so you have to solve this using javascript

Add this to the addittional attributes section of your drop down onchange="MyDateValidation();"
than goto the javascript section of your form an dcreate a new function.
There are a lot of these javascript examples to find on inet.

function MyDateValidation()
{
var mydropvalue = document.getElementById('myDropdownfieldname').value;
var myArrivelDate = document.getElementById('myArrivalfieldname').value;

if (mydropvalue.match('White') )
{
if ( (
myArrivleDate > 01-11-2013 && myArrivleDate < 30-11-2013
)
&& (
myArrivleDate > 01-04-2014 && myArrivleDate < 30-04-2014
)
)
// tell the customer what is wrong by adding your own text
// this is displaying a windows popup where user have to click "OK"
alert ('your own text'); //which should be goog validation
//for testing reasons use it, after testing comment out by using // before alert
else
{
alert ('your own other text'); //which should be wrong validation
//set the value of myArrivelDate back to null
document.getElementById('myArrivalfieldname').value='';
}
}
elseif (mydropvalue.match('Black') )
{
// do the same trick
}
else
{
// do the same trick
}
}