Simple multiplication progran help needed

Hi I just started playing around with Visual Basics and I tried to make a simple program to work out a price on a square item of steel, but I'm stuck.
The program has to multiply the length, width, thickness, the rate, and the mass 8.3 rounded off standard and then decided by 100000 to get rid of all the 0's.
So If we have a 300 square plate that's 12mm thick the calculation will be 300 x 300 x 12 (thickness) x 12(rate in Rands) x 8.3 (constant) / 1000000 the answer will be 107.568.
Please help me this is what I have done.

Public Class Form1

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim num1, num2, num3, num4, num5, num6, product As Single
num1 = TextBox1.Text
num2 = TextBox2.Text
num3 = TextBox3.Text
num4 = TextBox4.Text
num5 = Val(8.3)
num6 = Val(1000000)
product = num1 * num2 * num3 * num4 * num5 / num6


End Sub