CreateWindow Type Error

#include <Windows.h>

//Forwards Declarations
bool InitMainWindows(HINSTANCE, int);
LRESULT CALLBACK MsgProc(HWND, UINT, WPARAM, LPARAM);

//Constants
const int WIDTH = 800;
const int HEIGHT = 600;

HWND hwnd = NULL;//Handle to window

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow){
    return(1);
}

bool InitMainWindow(HINSTANCE hInstance, int nCmdShow){

    //Inital structure setup
    WNDCLASSEX wcex;
    wcex.cbSize = sizeof(wcex);
    wcex.style = CS_HREDRAW | CS_VREDRAW;//Set to redraw on resize

    //0 extra bytes if data
    wcex.cbClsExtra = 0;
    wcex.cbWndExtra = 0;

    wcex.lpfnWndProc = MsgProc;

    wcex.hInstance = hInstance;//Set handle for window

    wcex.hIcon = LoadIcon(NULL, IDI_APPLICATION);//Set App icon to defualt
    wcex.hCursor = LoadCursor(NULL, IDC_ARROW);//Set defualt cursor
    wcex.hbrBackground = (HBRUSH)GetStockObject(NULL_BRUSH);//Set app background intialy
    wcex.lpszClassName = "HelloDirectXClass";
    wcex.lpszMenuName = NULL;
    wcex.hIconSm = LoadIcon(NULL, IDI_WINLOGO);


    if (!RegisterClassEx(&wcex)){//If window structure fails to load program will exit
        return false;
    }

    //Create the window
    hwnd = CreateWindow(
        "HelloDirectXClass",//Class name, defined above
        "Hello DirectX",//Top bar title
        WS_OVERLAPPED | WS_SYSMENU, WS_CAPTION,//Window style, using default
        GetSystemMetrics(SM_CXSCREEN) / 2 - WIDTH / 2,//Position relitive to top left corner, X CXSCREEN notice the CX<--for X or width
        GetSystemMetrics(SM_CYSCREEN) / 2 - HEIGHT / 2,//Position relitive to top left corner, Y CYSCREEN notice the CY<--for Y or height
        WIDTH,
        HEIGHT,
        (HWND)NULL,//Setting window parent
        (HMENU)NULL,
        hInstance,//Window instance defined above
        (LPVOID)NULL);

    if (!hwnd){//Check if window exists
        return false;//If not exit program
    }

    ShowWindow(hwnd, nCmdShow);
}