var isNN = navigator.appName.indexOf("Netscape")!=-1; 

        function autoTab(input,len, e) {
                if(IsNumeric(input.value)==false)
                {
                 input.value='';
                alert('Not Valid');
               
                return;
                }
       

                 var keyCode = (isNN) ? e.which : e.keyCode;

                 var filter = (isNN) ? [0,8,9] : [0,8,9,16,17,18,37,38,39,40,46];

                 if(input.value.length >= len && !containsElement(filter,keyCode)) 
                 {

                 input.value = input.value.slice(0, len);

                 input.form[(getIndex(input)+1) % input.form.length].focus();

        }

         function containsElement(arr, ele) 
         {

                     var found = false, index = 0;

                     while(!found && index < arr.length)

                     if(arr[index] == ele)

                     found = true;

                     else

                     index++;

                     return found;

         }
                
		function IsNumeric(sText)
		{
			        var ValidChars = "-0123456789";
			        var IsNumber=true;
			        var Char;         
			        for (i = 0; i < sText.length && IsNumber == true; i++) 
			        { 
				        Char = sText.charAt(i); 
				        if (ValidChars.indexOf(Char) == -1) 
				        {
					        IsNumber = false;
				        }
			        }
			        return IsNumber;       
		}

         function getIndex(input) 
         {

                 var index = -1, i = 0, found = false;

                 while (i < input.form.length && index == -1)

                 if (input.form[i] == input)index = i;

                 else i++;

                 return index;

                 }

                 return true;
        }