Diagnosis
When maintaining sub-keys for a screen field (key field) to which amatchcode object is assigned, you specified a field ID which does notcorrespond to any matchcode object field.

System Response
Since a field ID is required to achieve the assignment between a fieldof the selected matchcode record and the screen field destined toreceive its value, the system rejects the field ID.

Procedure
Assign a field ID which belongs to a matchcode object field.
For further information about matchcode sub-keys, use F1 help for thefields Field ID and Sub-key field name.