$(document).ready(function(){					
					/*SET FOCUS*/
					$('#first_element, #orderRef').focus();
				
				
					/*PRODUCT SELECT*/
					$('.credit_txt').each(function() { 
			             $(this).keyup(function(){  
			                 calculateSum();  
			             });  
			        });  
			        
			   			        
			         function calculateSum() {
					         var sum = 0;  
					         //iterate through each textboxes and add the values  
					         $('.credit_txt').each(function() {
					             //add only if the value is number  
					             if(!isNaN(this.value) && this.value.length!=0) {  
					                 sum += parseFloat(this.value);  
					             }  
					         }); 
					         
					        if(sum > 0 && sum != ''){
					        	$('#order_submit').removeAttr("disabled");
					        }else $('#order_submit').attr("disabled","disabled");							 
					 }	

					 
					$('#orderRef').blur(function(){
						var length = $('#orderRef').val().length;	
						if(length < 1){
							$('#validation_result').replaceWith('<td id="validation_result"><font color="red">Order reference must not be left blank!</font></td>');
							$('#order_submit').attr("disabled","disabled");
						}
						else{
							$('#order_submit').removeAttr("disabled");							
							$('#validation_result').replaceWith('<td id="validation_result"><strong><font color="green">OK</font></strong></td>');

						}				
					});
	
					$('#orderRef').keyup(function(){
						var length = $('#orderRef').val().length;	
						if(length < 1){
							$('#validation_result').replaceWith('<td id="validation_result"><font color="red">Order reference must not be left blank!</font></td>');
							$('#order_submit').attr("disabled","disabled");
						}
						else{
							$('#order_submit').removeAttr("disabled");							
							$('#validation_result').replaceWith('<td id="validation_result"><strong><font color="green">OK</font></strong></td>');

						}				
					});
				});