Thread: Problem creating a Dialog Box

This is giving me an error 'Invalid Window Handle' but I can't figure out why.

Code:

LRESULT CALLBACK MainWinProc(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam)
{
    switch (Msg)
    {
        case WM_CREATE:
        {
            char str[80];
            if (DialogBoxParam(GetModuleHandle(NULL),
                               MAKEINTRESOURCE(IDD_NEWUSER),
                               hWnd,
                               NewUserDlgProc,
                               (LPARAM)str) <= 0)
            {
                ShowWinError();
            }
        }
        break;
 
        case WM_CLOSE:
        DestroyWindow(hWnd);
        break;
 
        case WM_DESTROY:
        PostQuitMessage(0);
        break;
 
        default:
        return DefWindowProc (hWnd, Msg, wParam, lParam);
    }
    return 0;
}

I am tring to opn a dialog for the user to enter a user name and have the dialog pass that back to the main window

The call to DialogBoxParam is throwing the invalid handle error. Any ideas?