Hi there,
I'd like to be sure of what you want, is the amount of the order specified by the client? If so, you'll have to create a new order based on the information given and in this case it's doesn't matter what kind of fields you are using since you'll have to submit a form to create this order.
However, if you plan to create the orders by yourself, I would advise you to give your client informations to login and redirect them to the order management view in the user panel. There, with the "Payment of orders not paid immediately" option activated, they will be able to pay for the order you created.
I hope, it helped, do not hesitate to ask if have more questions