Aunque simplificando podrias hacer esto :
Código vb.net:
Ver originalPublic Sub okcancelar()
Dim cnn As New SqlConnection
cnn.ConnectionString = Me.conn.ConnectionString
Dim query As String = "UPDATE c_albven SET libre_1 = 'Ok.' WHERE letra = 'CC' or letra = 'CB' or letra = 'CA'"
Dim cmd As New SqlCommand(query,cnn)
cnn.Open()
MessageBox.Show("No Actualizas")
Me.RichTextBox1.Text = " Facturas Canceladas en Ok."
cmd.ExecuteNonQuery()
cnn.Dispose()
End Sub