decrease the value in label when i click button.

Hi there.

code i.e given above it correct but better you implement this logic in javascript. if your requirement is like that then no issue.

I don`t understand why do you need TextBox, but this code allow you to count down when you click.
Add button and label to form.

 ushort val;       
        public Form1()
        {
            InitializeComponent();           
            val = 150;
            label1.Text = val.ToString();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            val--;
            label1.Text = val.ToString();
        }