C# Definition:

delegate IntPtr HookProc(int code, IntPtr wParam, IntPtr lParam);

VB Definition:

'Generic signature
Private Delegate Function HookProc(ByVal code As Integer, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As Integer

Notes:

MSDN documentation about HookProc : https://docs.microsoft.com/en-us/windows/win32/api/winuser/nc-winuser-hookproc