Simple javascript calculate form

I want 2 simple javascripts/jquery : I attached here with a file calculate6.html. The 1st javascript : When the user change the field qty or price, the field subtot and grdtot were updated. The subtot field should be automatically being calculated, however, it should be EDITABLE. In my example, when the user change the value of the subtot, the grdtot was not updated. What you need to do is to make this grdtot being updated when the user change the value of subtot manually (and added the balance b/f, 501.02 in this example). There were 2 lines in this example file, however, you code should work with more than 2 lines, may be upto 500lines. The 2nd javascript : When the user change the field qty or price, the field subtot and grdtot were updated. The subtot and grdtot fields should be automatically being calculated, and it should be NOT editable. What you need to do is to change this 2 fields from input field into a div just display the calculated values. this grdtot is total of subtot and added the balance b/f, 501.02 in this example. There were 2 lines in this example file, however, you code should work with more than 2 lines, may be upto 500lines.