function onEdit(event)
{
 var sheet = event.source.getActiveSheet();;
 var cRow = event.range.getRow();
 var program = sheet.getRange("A2:A");  
 var fRow = program.getRow();
 var lRow = program.getLastRow();

 if (event.range.getColumn()==1)
  {
   var values = event.range.getValues();
   for (var i in values)
    {
     var row = values[i];
     for (var j in row)
      {
       if (values[i][j]=="ON")
        {
         for (var a = fRow; a <= lRow ; a++) 
          {
           if (a!=cRow)
            {
             sheet.getRange(a,1).setValue ("OFF");
            }
          }
        }
      } 
    }
  }
}