Package No on Invoice

Hi all,

let the qty in Sales order is 10 and no. of packages also 10,in one more field i.e. UDF clinet want that it will display 1 to 10

and if the qty of 2nd row i.e. Item 2 is 20 and packages=20 ,in other UDF field it will display like-- 10 to 30.

simlarrly for other items.

How to do this in SAP .

Regards,

Neetu