wieso funktioniert dieser code denn nicht????

#include <iostream>
#include <windows.h>

using namespace std;

int _WindowsWait(char* Fenstername);

int main(void)
{
    HWND hWnd;
    _WindowsWait("Unbenannt - Editor"); 
    Sleep(100);
    hWnd = FindWindow(0,"Unbenannt - Editor");
     if(!hWnd)
       cout << "Error...\n";
    Sleep(100);
    //SendMessage(hWnd,WM_SETTEXT,0,(LPARAM)"hallo!");
    SendMessage(hWnd,WM_KEYDOWN,'a',1);
    //SendMessage(hWnd,WM_CHAR,'a',1);
    Sleep(1000);
    SendMessage(hWnd,WM_KEYUP,'a',1);
   return 0;
}

int _WindowsWait(char* Fenstername)
{
    cout << "Searching...\n";
    int a = 0;
    HWND hwnd;
    while(a < 1)
    {
    hwnd = FindWindow(0,Fenstername);
    if(!hwnd)
       a = 0;  
    else
    {
       a = 1;
       cout << "Success...\n";
    }
    Sleep(10);
    }
}

PostMessage(hWnd, WM_LBUTTONDOWN, 0, MAKELPARAM(10,10));

EDIT: Das würde dann einem Linksklick ('down') an der Koordinate K(10|10) .