I have a form named Main and one named order details. On the main form I have a listbox with displays general info about the order. When a user clicks on the order it opens the order details. On the main form I have a sub that sums the sales tax, unit price and total price. I am having problems with this. I need to have the sub update the totals when I add an item to the listbox. Where would the best place to put the sub be? I thought about putting it in the order details form instead of the main form. I declared the sub public but I don't know how to call it in another form.