[*-)]simple product calculation problem

HI!..

i have too calculate a total price by the multiplication of quanity and unit price in my web application..

the qty and unit price are entered in text boxes and total is diplayed in a label
protected void UPriceTextBox_TextChanged(object sender, EventArgs e)
{
TPriceLabel.Text = Convert.ToString((Convert.ToDouble(QtyTextBox.Text)) * (Convert.ToDouble(UPriceTextBox.Text)));
}

and the same for when qty text box is changed..

the problem is  total shud be dispalyed a ...