class myClass
    {
       public delegate void OverTheLimitDlg(int arg);
       public event OverTheLimitDlg OverTheLimit;
       public myClass()
       {
           myValue = 0;
       }
       private int myvalue = 0;
       public int myValue
       {
          get { return myvalue;}
          set
          {
             myValue = value;
             if(value > 5)
                OvertheLimit(value);
          }
        }
    }

myClass myObj;

private void Form_Load(object sender, EventArgs e)
{
   myObj = new myClass();
   myObj.OverTheLimit += SubsMethod;
   backgroundworker.RunWorkerAsync();
}
backgroundworker_DoWork(...)
{
   myObj.myValue = 10;
   //Some expressions.
}

private void SubsMethod(int someInt)
{
   myLabel.Text = "Oh it's over the limit!";
}