Set Amount in Opportunity Product with javascript

Hi there! In CRM 2011, in the Opportunity Product form, there are some default read-only fields named "Amount" and "Extended Amount".

If the opportunity revenue is set to "System Calculated", then the "Amount" field of the Opportunity Product is calculated by the system.

If the opportunity revenue is "User Provided", the "Amount" field in the Opportunity Product is still read-only but it is never updated.

I wanted to add some javascript to show the total to the user in the "Amount" field, but even with javascript the field is not saved, although its value gets updated on the form and I didnt forget the setSubmitMode("always") part.

Is there a way to achieve that?