Updating A Column By The Value Of '1'

Hi,
Its probably simple but.. 
How do I update a column by just '1'..
for example - heres my code:
    protected void Button1_Click(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection();
        con.ConnectionString = "HiddenConnection";


        con.Open();

        SqlCommand command = new SqlCommand();
        command.Connection = con;
        Label productIDLabel = (Label)DataList1.FindControl("productIDLabel");

        command.CommandText = "UPDATE Items SET numberclickedin = numberclickedin + 1 WHERE productID=@productID";
        command.Parameters.Add("@productID", productIDLabel.Text);
        command.ExecuteNonQuery();

        con.Close();
        command.Dispose();
    }
 
As you can see in the bold text, I want to add 1 to the numberclickedin column.. and in my primative way Ive just typed +1
What should I use instead?
Thanks in advance,
Jon