Set the in-built MT4 price alarm by dragging a script into a chart

Hello,

I need a script which I drag into the chart and then the in-built MT4 price alarm should be set.

The script should start like this:

//+------------------------------------------------------------------+
//| Script program start function                                    |
//+------------------------------------------------------------------+
void OnStart()
  {
   double price = WindowPriceOnDropped();
   
   [... your code ...]

  }

This price must be the alarm price level.

I can code some mql4-stuff but I think for this project it is necessary to know a lot about user32.dll and other Win32 API things.

Just to be very clear, I am talking about these alerts: https://www.metatrader4.com/en/trading-platform/help/overview/terminal/terminal_alerts