function add_input_field(field){
		
			var container = document.getElementById('container_'+field);
			var record_elems = container.childNodes;
			var num_records = record_elems.length;
			
			/* clone existing record */
			var src_record = record_elems[num_records-1];
			var new_record = src_record.cloneNode(true);
			
				/* empty & update cloned record */
				new_record_count = parseInt(num_records);
				var num_digit = parseInt(new_record_count-1).toString().length
				var str = new_record.id;
				new_record.id =  str.substring(0,str.length-parseInt(num_digit))+new_record_count;
				
				/* input elements */
				input_elems = new_record.childNodes;
				var num_input = input_elems.length;
				for(i=0;i<num_input;i++){
					if(input_elems[i].nodeType==1 && 
						(input_elems[i].nodeName.toUpperCase()=='INPUT' || 
						input_elems[i].nodeName.toUpperCase()=='SELECT' || 
						input_elems[i].nodeName.toUpperCase()=='TEXTAREA')){
						
						input_elems[i].value= '';
						var str = input_elems[i].id
						input_elems[i].id = str.substring(0,str.length-parseInt(num_digit))+new_record_count;
						input_elems[i].name = str.substring(0,str.length-parseInt(num_digit))+new_record_count;
					}
					
				}
				
			/* add new record */
			container.appendChild(new_record);
		}