The error message linking is a feature of WebDynpro Floorplan Manager. Basically the UIBB (or the feeder class of a GUIBB) provide the message and field name(s) the message is connected to. The WebDynpro runtime then does the rest.
For the check BAdi, this facility is exposed in IF_EX_USMD_RULE_SERVICE~CHECK_ENTITY( ) via the structure of the return message table ET_MESSAGE:
- The MSGxxx fields take the parameters of a standard T100 message (like message class, number, ...)
- FIELDNAME contains the name of the field to highlight
- The mapping should then be done by the MDG framework, mapping Entity (IV_ENTITY) + FIELDNAME to the UIBB(s) where the field is visible
Only problem is it does not work, at least not in my tests with MDG-Mv7SP03.