update using stringbuilder.append and doing operation

Question

Hello everybody, I need your help on this problem, see...

 

Public Sub updateRequisicaoItemBar(ByVal r_id As Integer, ByVal qt As Integer, ByVal price As Double) 

Dim sqlBuilder As New System.Text.StringBuilder()

With sqlBuilder

.Append("update tbl_Stock  set ")

.Append("qtyEnviar='" & CDbl(.Append("qtyEnviar").ToString) + qt - CDbl(.Append("qty").ToString) & "',")

.Append("qty='" & qt & "',")

.Append("PU='" & preco & "'")

.Append("valor='" & (.Append("qty").ToString * price) & "',")

.Append("sent='" & 0 & "'")

.Append(" where id='" & r_id & "'")

End With

Using cn As SqlConnection = New SqlConnection(getConnectionStringFinance())

Try

cn.Open()

Using cm As SqlCommand = New SqlCommand(sqlBuilder.ToString, cn)

cm.ExecuteNonQuery()

MessageBox.Show("Updated")

End Using

Catch ex As Exception

MessageBox.Show(ex.ToString)

End Try

End Using

End Sub

 

 The red lines seem not doing in the right way, what the right way doing this. please help