Undefined (Win32) Externals

[Loopback]

Hi!

Let me begin by saying, that I haven't used Usenet newsgroup at all, so 
please excuse me for any errors or misunderstandings of the guidelines.

I recently begun programming a win32 application though I instantly got 
stuck with a problem. As you might know, win32 applications require that 
you define the WindowProc function for processing window messages.

I've used a object-oriented approach for this, and that requires that 
you declare the WindowProc function as static, and bind your own class 
(hWnd) to GWL_USERDATA, to be able to call your own, class defined, 
message handler (WindowProc). To do this, you have to access the two 
functions GetWindowLong and SetWindowLong.

For some reason, these functions do not exist in the windows module 
(std.c.windows.windows), neither does the GWL_USERDATA constant.

To solve this I've used this alternative code:

extern (Windows)
{
	int GWL_USERDATA;
	LONG SetWindowLong(HWND, int, LONG);
	LONG GetWindowLong(HWND, int);
}

When I then try to compile this application, the GWL_USERDATA constant 
compiles without any errors, but the Get-/SetWindowLong produces linker 
errors.

To solve the linker errors, I checked which library they were contained 
in, on MSDN it said User32.lib. Therefore I linked to this library - 
without any success.

So to summarize, how do I solve these linker errors:

Error 42: Symbol Undefined _SetWindowLong at 12
Error 42: Symbol Undefined _GetWindowLong at 8

Sorry for such a long message!
Any help is greatly appreciated!