Update release order va01 based on contract va41

Hi Experts,

I have a requirement where there is a checkbox (custom) in the tab Additional data A in VA41. If the user unchecks this and saves the contract, the change should also be reflected in the corresponding release documents of this contract. I have found user exit USEREXIT_SAVE_DOCUMENT_PREPARE.

I want to know how to achieve this. How will the data be linked between contract and release order.

Please advise.