Lanham EDI 856 Cancellation Issue

Hi,

I am working on Lanham EDI module. when I receive 850 to create sales order it's works fine and to send advance shipment notice I created EDI 856 document which also works fine. But, I am not able to handle cancellation scenario with 856 file. below is the item line detail segment for both shipment and cancel line.

EXAMPLE:
SHIPMENT: SN1**3*EA*****AC This works
CANCEL: SN1**0*EA**3*EA**ID This I am not able to map with segment

thanks!