Here I’ve entered the Item Number, Quantity, Product ID, the Width and Height. As soon as I’ve entered the height and tabbed out of it the system has automatically calculated the value of square metre, the item price, VAT and the amount (which is the Item Price and the VAT added). Below this the Total, Discount, Invoice Total and the Sterling Amount are still blank, these will remain like this until I’ve tabbed out of the sub-form.