I had cistomized the contract management by adding an options for product price in one2many fields. Right now, I already can generate sale order from this contract by using a new button at the contract's view But, my problem is, my generated sale order have empty order lines. It didn't get the values which defined on the contract.

The concept is exactly same as when we want to generate an invoice from sale order but I'm little bit struggle to do this. 

Can anyone give me any tips on how to solve this problem?