From ReliCodia

ATOM RegisterClassEx (WNDCLASSEX const * winClass);
ATOM RegisterClass (WNDCLASS const * winClass); (obsolete)

Registers window class, described by the structure WNDCLASSEX, with the Windows system. Once the class is registered, it can be addressed using its name (a string) or the ATOM returned by this API.

A window class is used in the creation of windows through the CreateWindowEx API. All windows of the same class share certain visual characteristics described in WNDCLASSEX, as well as behavior, described by Window Procedure (also part of WNDCLASSEX).


RegisterClassEX can be called from Visual Basic using the following declaration