You need to setup a TimerProc callback
PHP Code:
[i]From MSDN[/i]
VOID CALLBACK TimerProc(
  
HWND hwnd,         // handle to window
  
UINT uMsg,         // WM_TIMER message
  
UINT_PTR idEvent,  // timer identifier
  
DWORD dwTime       // current system time
); 
Then pass the address of TimerProc into SetTimer.