sales return with reference to billing for the 2nd time is accepted?

Hi Gurus,

This is the scenario I am working...

It is as follows:

1. Sales order is generated for QTY 10

2. deliver done for QTY 10

3. billing done for QTY 10

4. Sales return done for QTY 10 with reference to billing

5. delivery and billing done for sales return QTY 10

now the cycle is finished

if i do again sales return with reference to billing it is accepting

hw can we approach to this issue?

plz suggest.

Regards,

Anbu