Customizations required on Negotiation Form

Hello,

We have a requirements to customize the standard fields and i need to know whether we can achieve it or not.

On the negotiation creation form in the Lines section, we need to make the quantity and requested delivery date fields as read only based on the condition that whether it is backed by a requisition or not. Now I've tried to make the field as read only but I couldn't find any binding params that I can use to cater this requirement. Please advise whether it can be achieved or not?

Please provide a solution to this requirement.