function calculate_registration_cost(){
	var cost_ex_vat = parseInt(document.registerinterest.course_cost.value);
	var current_cost = 0;
	var current_cost_inc_vat = 0;
	var delegate_count = 1;
	var i = 1;
	var field;

	do {

		field = "delegate_name_"+i;
		if(!document.getElementById(field))
			break;

		date_field = "course_date_"+i;
		job_title_field = "job_title_"+i;

		if(document.getElementById(field).value.length > 0 ||
		   document.getElementById(date_field).value.length > 0 ||
		   document.getElementById(job_title_field).value.length > 0) {
		   	current_cost += cost_ex_vat;
		   	delegate_count++;
		}
		i++;
	}while(1);

	if(current_cost > 0){
		current_cost_inc_vat = current_cost * 1.175;
	}
	document.getElementById("cost_ex_vat").innerHTML = "£" + current_cost.toFixed(2);
	document.getElementById("cost_inc_vat").innerHTML = "£" + current_cost_inc_vat.toFixed(2);
}