// Populates the trip dropdown according to the trips array
function countryChanged(dropDown)
{
    var tripBox = document.forms[0].trip;
    var i = dropDown.selectedIndex-1;
    tripBox.disabled = (i == -1);
    tripBox.selectedIndex = 0;
    if(i >= 0)
    {
        for(j=0; j<trips[i].length; j++)
        {
            tripBox.options[j+1] = new Option(trips[i][j],trips[i][j]);
        }
    }
    for(k=j+1; k<tripBox.length; k++)
    {
        tripBox.options[k] = null;
    }
    if(typeof(tripChanged) != 'undefined')
    {
        tripChanged(tripBox);
    }
}