How can I maximize an IE window created by VBA with SHDocVw.InternetExplorer command?

This could be done like this as well.

ie.FullScreen = True

or

ie.TheaterMode = True

Then you don't to declare a function.

For Internet Control, there's no inherent Window property. You need to use WinAPI.

This code will work :

'/ Win API declaration
Private Declare Function ShowWindow Lib "user32" _
         (ByVal hwnd As Long, ByVal nCmdSHow As Long) As Long
        Const SW_SHOWMAXIMIZED = 3

Sub wpieautologin()

Dim ie As SHDocVw.InternetExplorer

Dim NOME_EMPRESA, CNPJ, CPF, COD_ACESSO As String
Dim Lookup_Range As Range

Set ie = New SHDocVw.InternetExplorer
ie.Visible = False

ie.Navigate "http://www8.receita.fazenda.gov.br/simplesnacional/controleacesso/autentica.aspx?id=6"



'// rest of your code....


'/ Win API to maximize it.
'/ Visible prop not required anymore
ShowWindow ie.hwnd, SW_SHOWMAXIMIZED
End Sub

Check other window state at : http://www.techrepublic.com/blog/10-things/10-plus-of-my-favorite-windows-api-functions-to-use-in-office-applications/