This correct seems to have solved the problem, thanks guys
<pre lang="cs">private void textBox9_TextChanged(object sender, EventArgs e)
{
if ((string.IsNullOrWhiteSpace(textBox9.Text)))
{
textBox2.Text = "";
textBox4.Text = "";
textBox10.Text = "";
textBox6.Text = "";
textBox12.Text = "";
textBox11.Text = "";
textBox14.Text = "";
textBox13.Text = "";
textBox16.Text = "";
}
else
{
range = Convert.ToDouble(textBox9.Text.Trim());
MaxC = Math.Round((CVAL * (1 + range)), 3);
MinC = Math.Round((CVAL * (1 - range)), 3);
MaxP = Math.Round((pVAL * (1 + range)), 3);
MinP = Math.Round((pVAL * (1 - range)), 3);
Maxsi = Math.Round((siVAL * (1 + range)), 3);
Minsi = Math.Round((siVAL * (1 - range)), 3);
Maxsc = Math.Round((scrap * (1 + range)), 3);
Minsc = Math.Round((scrap * (1 - range)), 3);
Maxtemp = Math.Round((temp * (1 + range)), 3);
Mintemp = Math.Round((temp * (1 - range)), 3);
textBox2.Text = Convert.ToString(MaxC);
textBox4.Text = Convert.ToString(MinC);
textBox10.Text = Convert.ToString(MaxP);
textBox6.Text = Convert.ToString(MinP);
textBox12.Text = Convert.ToString(Maxsi);
textBox11.Text = Convert.ToString(Minsi);
textBox14.Text = Convert.ToString(Maxsc);
textBox13.Text = Convert.ToString(Minsc);
textBox16.Text = Convert.ToString(Maxtemp);
textBox15.Text = Convert.ToString(Mintemp);
}