SAP Note 28066 - ME90, MB90: No F4 help for message type

Symptom:

On the selection screens of transactions ME90 (Print/Transmit Messages: Purchasing Documents) and MB90 (Inventory Management Message Processing), there is no "possible entries" pushbutton (F4) on the field 'Message type'.

Cause and prerequisites

Parameter P_KSCHL refers to the field NAST-KSCHL, for which the foreign is not maintained. If you maintain the foreign key, however, all messagetypes for all applications are displayed. This is of limited use to the user.
A sensible F4 help for the field "message type" (and, incidentally, alsofor the field "message application") is not available until Release 3.0B. It uses the new ABAP language element
AT SELECTION-SCREEN ON VALUE-REQUEST (new as of 3.0). This F4 help cannot therefore be installed in existing 2.2 releases.

Solution
The only solution for 2.2 is to maintain the foreign key for the database field NAST-KSCHL. The checking table has already been entered in the Data Dictionary; the foreign key need only be saved.

Additional key words

P_KSCHL, NAST-KSCHL