diff --git a/include/hook.h b/include/hook.h
index b9ea056..f3ffd54 100644
--- a/include/hook.h
+++ b/include/hook.h
@@ -9,12 +9,29 @@
 
 #include "windows.h"
 
-#define HOOK_WIN16	0x0
-#define HOOK_WIN32A	0x1
-#define HOOK_WIN32W	0x2
+#define HOOK_WIN16	0x00
+#define HOOK_WIN32A	0x01
+#define HOOK_WIN32W	0x02
+#define HOOK_INUSE	0x80
+
+typedef struct
+{
+   LPARAM   lParam;
+   WPARAM16 wParam;
+   UINT16   message;
+   HWND16   hwnd;
+} CWPSTRUCT16, *LPCWPSTRUCT16;
+
+typedef struct
+{
+  LPARAM        lParam;
+  WPARAM32      wParam;
+  UINT32        message;
+  HWND32        hwnd;
+} CWPSTRUCT32, *LPCWPSTRUCT32;
 
 /* hook type mask */
-#define HOOK_MAPTYPE (3)
+#define HOOK_MAPTYPE (HOOK_WIN16 | HOOK_WIN32A | HOOK_WIN32W)
 
 extern HOOKPROC16 HOOK_GetProc16( HHOOK hhook );
 extern BOOL32 HOOK_IsHooked( INT16 id );