Im building an order form.

Items are displayed as radio buttons, check boxes and drop down menus and priced individually.
E.g. Dropdown menu:
Item 1 £45.00
Item 2 £49.00
Item 3 £62.00

There are around a dozen or more items.

I need the customer to be able to pay a 50% deposit at form submission. Im using paypal for payments.
So I need paypal to bill for just 50% of the total cost of the order form.


How do I do this and pass just 50% of the total to PayPal ? ...divide the total value by 2 for paypal?
How do I show the customer the calculated 50% total ? so the amount they will be paying as a deposit?

I should add that the dozen or so items are listed separately.
So there are say 3 options in a dropdown, then two items in radio buttons, 3 items in another dropdown etc....

Its not a dozen items all in the same menu field.

So Im hoping there is an option to edit the amount generated as the total, instead of me having to code for each of the field options individually

Have you looked at the many calculation form examples I've done?