Dear Pranshu ,
As per my knowledge you can do through user exit and before that just think any impact is there for other material in the future or you want to extend for other materials. this may affect .
Write the logic for Sales order line item in MV45AFZZ program .
there is 2 materials ==== A & B
if in line item 10 and material is A --- then logic in the program has to update the material name in header additional TAB A or B in any field after entering the material in any line item and don't hardcode that material name in your program . just link with any dynamic table so that in future if you want to extend any other material it will help you .every time logic will check with dynamic table if it matches then it will update other wise ignore .
now for line item 20 material is B -- in you pricing procedure, you have to add that HEADER ADDITIONAL TAB FEILD to you access sequence . so that when ever if you enter this material A automatically it will update to header level and in your access sequence you have to add with material and additional tab and other required combination with 60% discount .
Regards,
C.B Reddy.