Several Queries

It would be very helpful if someone could help me with a few problems I am having with my program:

- I have a form that needs to calculate the the total cost. There is list box that has all the prices in for items in a order, I would like all these prices to be added up and shown in a total price text box so that when new prices are added and prices are removed the total price stays updated with the correct total. How can this be done?

- I then want the items from my items ordered and price list boxes, the current date and the total price to be shown on a new invoice form when a command button is pressed. How can this be done?

- Finally I then want this invoice form to have a Print command button that when pressed will print the form and add the date and total price to a serial file. How can I do this?

I'm really stuck with this and I have no idea, any help would be greatly welcome.

Thanks