diff --git a/win32ss/include/callback.h b/win32ss/include/callback.h
index 4c4d56323f0..9fdf265ba59 100644
--- a/win32ss/include/callback.h
+++ b/win32ss/include/callback.h
@@ -1,27 +1,22 @@
-#ifndef __INCLUDE_USER32_CALLBACK_H
-#define __INCLUDE_USER32_CALLBACK_H
+/*
+ * PROJECT:     ReactOS Kernel
+ * LICENSE:     LGPL-2.1-or-later (https://spdx.org/licenses/LGPL-2.1-or-later)
+ * PURPOSE:     Defining kernel-to-user32 callbacks
+ * COPYRIGHT:   Copyright 2018 James Tabor <james.tabor@reactos.org>
+ *              Copyright 2024 Katayama Hirofumi MZ <katayama.hirofumi.mz@gmail.com>
+ */
 
-#define USER32_CALLBACK_WINDOWPROC            (0)
-#define USER32_CALLBACK_SENDASYNCPROC         (1)
-#define USER32_CALLBACK_LOADSYSMENUTEMPLATE   (2)
-#define USER32_CALLBACK_LOADDEFAULTCURSORS    (3)
-#define USER32_CALLBACK_HOOKPROC              (4)
-#define USER32_CALLBACK_EVENTPROC             (5)
-#define USER32_CALLBACK_LOADMENU              (6)
-#define USER32_CALLBACK_CLIENTTHREADSTARTUP   (7)
-#define USER32_CALLBACK_CLIENTLOADLIBRARY     (8)
-#define USER32_CALLBACK_GETCHARSETINFO        (9)
-#define USER32_CALLBACK_COPYIMAGE             (10)
-#define USER32_CALLBACK_SETWNDICONS           (11)
-#define USER32_CALLBACK_DELIVERUSERAPC        (12)
-#define USER32_CALLBACK_DDEPOST               (13)
-#define USER32_CALLBACK_DDEGET                (14)
-#define USER32_CALLBACK_SETOBM                (15)
-#define USER32_CALLBACK_LPK                   (16)
-#define USER32_CALLBACK_UMPD                  (17)
-#define USER32_CALLBACK_IMMPROCESSKEY         (18)
-#define USER32_CALLBACK_IMMLOADLAYOUT         (19)
-#define USER32_CALLBACK_MAXIMUM               USER32_CALLBACK_IMMLOADLAYOUT
+#pragma once
+
+#define DEFINE_USER32_CALLBACK(id, value, fn) id,
+
+typedef enum _USER32_CALLBACK
+{
+#include "u32cb.h"
+    USER32_CALLBACK_COUNT
+} USER32_CALLBACK;
+
+#undef DEFINE_USER32_CALLBACK
 
 typedef struct _WINDOWPROC_CALLBACK_ARGUMENTS
 {
@@ -230,5 +225,3 @@ NTSTATUS WINAPI
 User32CallImmProcessKeyFromKernel(PVOID Arguments, ULONG ArgumentLength);
 NTSTATUS WINAPI
 User32CallImmLoadLayoutFromKernel(PVOID Arguments, ULONG ArgumentLength);
-
-#endif /* __INCLUDE_USER32_CALLBACK_H */
diff --git a/win32ss/include/u32cb.h b/win32ss/include/u32cb.h
new file mode 100644
index 00000000000..168df49f7dc
--- /dev/null
+++ b/win32ss/include/u32cb.h
@@ -0,0 +1,28 @@
+/*
+ * PROJECT:     ReactOS Kernel
+ * LICENSE:     LGPL-2.1-or-later (https://spdx.org/licenses/LGPL-2.1-or-later)
+ * PURPOSE:     Defining kernel-to-user32 callback entries
+ * COPYRIGHT:   Copyright 2024 Katayama Hirofumi MZ <katayama.hirofumi.mz@gmail.com>
+ */
+
+/* DEFINE_USER32_CALLBACK(id, value, fn) */
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_WINDOWPROC,              0, User32CallWindowProcFromKernel)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_SENDASYNCPROC,           1, User32CallSendAsyncProcForKernel)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_LOADSYSMENUTEMPLATE,     2, User32LoadSysMenuTemplateForKernel)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_LOADDEFAULTCURSORS,      3, User32SetupDefaultCursors)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_HOOKPROC,                4, User32CallHookProcFromKernel)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_EVENTPROC,               5, User32CallEventProcFromKernel)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_LOADMENU,                6, User32CallLoadMenuFromKernel)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_CLIENTTHREADSTARTUP,     7, User32CallClientThreadSetupFromKernel)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_CLIENTLOADLIBRARY,       8, User32CallClientLoadLibraryFromKernel)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_GETCHARSETINFO,          9, User32CallGetCharsetInfo)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_COPYIMAGE,              10, User32CallCopyImageFromKernel)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_SETWNDICONS,            11, User32CallSetWndIconsFromKernel)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_DELIVERUSERAPC,         12, User32DeliverUserAPC)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_DDEPOST,                13, User32CallDDEPostFromKernel)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_DDEGET,                 14, User32CallDDEGetFromKernel)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_SETOBM,                 15, User32CallOBMFromKernel)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_LPK,                    16, User32CallLPKFromKernel)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_UMPD,                   17, User32CallUMPDFromKernel)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_IMMPROCESSKEY,          18, User32CallImmProcessKeyFromKernel)
+DEFINE_USER32_CALLBACK(USER32_CALLBACK_IMMLOADLAYOUT,          19, User32CallImmLoadLayoutFromKernel)
diff --git a/win32ss/user/user32/misc/dllmain.c b/win32ss/user/user32/misc/dllmain.c
index 3cc2b426a2e..c3c8451985a 100644
--- a/win32ss/user/user32/misc/dllmain.c
+++ b/win32ss/user/user32/misc/dllmain.c
@@ -203,30 +203,14 @@ UnloadAppInitDlls(VOID)
     }
 }
 
-PVOID apfnDispatch[USER32_CALLBACK_MAXIMUM + 1] =
+#define DEFINE_USER32_CALLBACK(id, value, fn) fn,
+
+PVOID apfnDispatch[USER32_CALLBACK_COUNT] =
 {
-    User32CallWindowProcFromKernel,
-    User32CallSendAsyncProcForKernel,
-    User32LoadSysMenuTemplateForKernel,
-    User32SetupDefaultCursors,
-    User32CallHookProcFromKernel,
-    User32CallEventProcFromKernel,
-    User32CallLoadMenuFromKernel,
-    User32CallClientThreadSetupFromKernel,
-    User32CallClientLoadLibraryFromKernel,
-    User32CallGetCharsetInfo,
-    User32CallCopyImageFromKernel,
-    User32CallSetWndIconsFromKernel,
-    User32DeliverUserAPC,
-    User32CallDDEPostFromKernel,
-    User32CallDDEGetFromKernel,
-    User32CallOBMFromKernel,
-    User32CallLPKFromKernel,
-    User32CallUMPDFromKernel,
-    User32CallImmProcessKeyFromKernel,
-    User32CallImmLoadLayoutFromKernel,
+#include "u32cb.h"
 };
 
+#undef DEFINE_USER32_CALLBACK
 
 VOID
 WINAPI