set running process on bottom

I'm new to C++ just started to learn and I'm trying to change the appearance of a running process for example "Calculator" to be always on bottom/on desktop but with no successes.

Here is the code I have so far:

#include "stdafx.h"
#include <windows.h>
#include <stdio.h>
#include <string>
#include <iostream>
using namespace std;

void set_to_bg() {
    LPCSTR app_name = "Calculator";
    HWND hWnd = FindWindowA(0, (app_name));
    HWND ProgmanHwnd = FindWindow(_T("Progman"), _T("Program Manager"));
    SetParent(hWnd, ProgmanHwnd);
    SetWindowPos(hWnd, HWND_BOTTOM, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE);
}

int main()
{
    set_to_bg();
}

What Happens is that the "Calculator" window disappears. I'm using Spy++ to monitor windows and I'v noticed that the "Calculator" is parented to "Program Manager" but it doesn't shows it. if I omit the "SetParent(hWnd, ProgmanHwnd);" the "Calculator" is shown and sets to bottom. When I open a folder or some other app they overlap the "Calculator" which is a good result but if I click the "Calculator" then it losses its "OnBottom" property and overlaps all the other folders or apps that opened.

Any ideas, code snippets, guidance would be very appreciated!