$(document).ready(function()
{
$("select#Messe").change(function ()
{
switch($("select#Messe").val())
{
case "Brille und Co":
$("select#Branche").html('');
break;
case "Innowa":
$("select#Branche").html(' ');
break;
case "Waesche und mehr":
$("select#Branche").html('');
break;
}
});
});