VL09 - Good movemt for delivery cannot be cancelled

Hi,

We have created a return delivery and PGR'd which created a material document.

I wanted to reverse it with VL09 but getting the error message as shown in following screen shot.

How to reverse now?

Tried using MBST, and getting the error

Please help me to cancell this material document to cancell the return delivery.

Thanks,

Venkat.