Get Line Items From One Table And Add Them To Another On Button Click

Hi,

I have a table that contains Orders and in that table is a sub-table Pricing which has to fields - Description and Price.
I have created another table named Invoices with a sub-table named Inv Pricing. In the Invoices table, you link to an order that you want to create the invoice for, from there I want to click a button that will pull in the line items from the Pricing table over in Orders and populate the Inv Pricing table.
Any help will be greatly appreciated.