Ok I fixed the error but the message box in the function is not showing up. Here is my code:
PHP Code:
//Includes
#include <iostream.h>
#include <windows.h>

//Globals
HWND myhwnd=FindWindow("ConsoleWindowClass"NULL);
//Function Prototypes
void sleep(int milliseconds);
VOID CALLBACK TimerProc(HWND hwndUINT uMsgUINT_PTR idEventDWORD dwTime);
int main()
{
    
SetTimer(myhwnd11000, (TIMERPROC) &TimerProc);
    
cout << "Hello." << endl;
    
MessageBox(myhwnd"Wow, I can make message boxes...haha""WEEEEE!!!"MB_OK MB_ICONSTOP);
    
cout << "Exiting in 2 seconds.\n";
    
//sleep(2000);
    
return 0;
}
void sleep(int milliseconds)
{
    
Sleep(milliseconds);
}
VOID CALLBACK TimerProc(
  
HWND hwnd,         // handle to window
  
UINT uMsg,         // WM_TIMER message
  
UINT_PTR idEvent,  // timer identifier
  
DWORD dwTime       // current system time
)
{
  
MessageBox(myhwnd"HELLO""HELLO"MB_OK);