Dear Murthy
You can achieve the requirement in two ways:
1. Create a Text-id in either header or Item level and ask the user to fill it up mandatorily. You may also mandate the text field so that it has to be filled compulsorily.
2. You may use any other field that is not used, such as Name field in Order data tab, ask your abaper to change the description of the field BNAME. It has data type Char and length 35, so that should be enough.
Later, you may create a report to show the Demand Quantity and Supplied Quantity.
Regs
Pronojit