Cursor old;
        private void Form1_Load(object sender, EventArgs e)
        {
            this.Cursor = Cursors.Hand;
            old = this.Cursor;
        }
        private void Form1_CursorChanged(object sender, EventArgs e)
        {
            if (old == Cursors.Hand && this.Cursor == Cursors.Default)
                MessageBox.Show("ok");
            
        }

        private void button1_Click(object sender, EventArgs e)
        {
            this.Cursor = Cursors.Default;
            old = this.Cursor;
        }