Creating a class module with my VBA code

Hi all,

I'm fairly new to class modules. I have the current code and need to create a class module of it. How can I do so? Thanks!

Sub Book1()

Dim i, j, k, rowcount As Integer

Dim net As Long

rowcount = 2
net = 0

While Worksheets("Sheet1").Cells(rowcount, 1) <> 0
rowcount = rowcount + 1
Wend

For i = 2 To rowcount

If Worksheets("Sheet1").Cells(i, 1) = "B" Then
    net = net + Worksheets("Sheet1").Cells(i, 2) * Worksheets("Sheet1").Cells(i, 3)
    
    Else
    
    net = net - Worksheets("Sheet1").Cells(i, 2) * Worksheets("Sheet1").Cells(i, 3)
    
End If

Next i

MsgBox (net)






End Sub