VA01 enhancement screen 8459 or 8460

Dear ALL

Now we want to add some fields into user exit screen 8459 or 8460 of program: SAPMV45A, about the screen flow logic, where we should include? into program SAPMV45A ? But now our client had some concern , this is the standard program , they do not allow us to change it, so change to program is necessary or not , if not , where we should include the coding?

and does anyone know any OSS notes about this? thanks a log

Best Regards

Jacky