Reason code required for movement type 122

I am getting the above error and looked up a thread on the forum which applies to my scenario. However there was a mention of defining a text schema and assigning it to the movemnt type. Can someone help me how to do that?

Jai

The thread is as follows:

We are running SRM 550 with Extended Classic scenario. When I attempt to create a return delivery, I get an error message saying: A reason has to be entered for movement type 122. But there is no way to enter the reason, i.e no fields or indicators.

<b>The text schema for return delivery is maintained and assigned to the document type for confirmations -</b> as far as I am aware this is all the config which is necessary to activate the reason for return delivery function. Am I missing something??