function requireSomeFields(form)
{
	var fieldNr = form.length; 	
	var message = "Enkele velden zijn verplicht om in te vullen en je bent iets vergeten in te vullen. Zou je dit als nog willen doen. Deze velden zijn rood omrand";
	var output  = false;
    
	for(i=0;i<fieldNr;i++)
	{
        var element = form.elements[i];
        
        //setting the initial state
		element.style.borderColor = "";	
        var theName = new String(element.name);
        
        
        //check for the fields that are required (note: these need a name starting with __ i.e. double underscore)
        if(theName.charAt(0) == "_" && theName.charAt(1) == "_") {
            if(element.value == undefined || element.value == "" )
            {
                alert(message);
                output = false;
                element.style.borderColor="#FF0000";
                element.focus();
                return false;
            } else {
                output = true;
            }
        }
    }
    return output;
}