findwindowex for html multiple windows

I have multiple IE windows open.  In one window are text field values that I want to copy to text fields in another window. For example, I want to copy from the First Name value from Form1 to FirstName field of Form2.  For simplicity assume a title of the windows are "Form1" and  "Form2" and the fields are FirstName and FirstName.  The following code that has a couple of problems.  

1) The code only works on the top most IE window. It can't find Form1 or Form2.

2) The Add_Get function currently only works if the passed value is strings contained in the call -  it will not work if  a variable is passed.  It will not work if as it is currently written. Not sure why.

‘//// Form
Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" ( _
    ByVal lpClassName As String, _
    ByVal lpWindowName As String) As Long
Private Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" ( _
    ByVal hWnd1 As Long, _
    ByVal hWnd2 As Long, _
    ByVal lpsz1 As String, _
    ByVal lpsz2 As String) As Long
Private Sub Command1_Click()
  Dim x As String
 
 
  '***********************
  ' Get the value from Form1
  '************************
 
  x = Add_Get(GetValue, "biFirstname")
     
  '***********************
  ' set the value in Form2
  '***********************

' this doen't work  

Call Add_Get(SetValue, "firstname", x)

'this works
Call Add_Get(SetValue, "lastname", "last name")
   
End Sub


‘//// Module 1
Option Explicit

Private Type UUID
  Data1 As Long
  Data2 As Integer
  Data3 As Integer
  Data4(0 To 7) As Byte
End Type

Public Enum IValues
    GetValue = 0
    SetValue = 1
End Enum

Private Declare Sub ZeroMemory Lib "kernel32.dll" Alias "RtlZeroMemory" ( _
    Destination As Any, _
    ByVal Length As Long)

Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" ( _
    ByVal lpClassName As String, _
    ByVal lpWindowName As String) As Long

Private Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" ( _
    ByVal hWnd1 As Long, _
    ByVal hWnd2 As Long, _
    ByVal lpsz1 As String, _
    ByVal lpsz2 As String) As Long

Private Declare Function ObjectFromLresult Lib "oleacc" ( _
    ByVal lResult As Long, _
    riid As UUID, _
    ByVal wParam As Long, _
    ppvObject As Any) As Long

Private Declare Function RegisterWindowMessage Lib "user32" Alias "RegisterWindowMessageA" ( _
    ByVal lpString As String) As Long

Private Declare Function SendMessageTimeout Lib "user32" Alias "SendMessageTimeoutA" ( _
    ByVal hWnd As Long, _
    ByVal Msg As Long, _
    ByVal wParam As Long, _
    lParam As Any, _
    ByVal fuFlags As Long, _
    ByVal uTimeout As Long, _
    lpdwResult As Long) As Long

Private HtmlDoc As HTMLDocument

Private Function Generate(ByVal hWnd As Long) As IHTMLDocument

  Dim ID     As UUID
  Dim lngReg As Long
  Dim lngHnD As Long

  lngHnD = RegisterWindowMessage("WM_HTML_GETOBJECT")

  With ID
    .Data1 = &H626FC520
    .Data2 = &HA41E
    .Data3 = &H11CF
    .Data4(0) = &HA7
    .Data4(1) = &H31
    .Data4(2) = &H0
    .Data4(3) = &HA0
    .Data4(4) = &HC9
    .Data4(5) = &H8
    .Data4(6) = &H26
    .Data4(7) = &H37
  End With

  Call SendMessageTimeout(hWnd, lngHnD, 0, 0, &H2, 2000, lngReg)
  Call ZeroMemory(ID, Len(ID))
  Call ObjectFromLresult(lngReg, ID, 0, Generate)

End Function

Public Function Add_Get(IQuery As IValues, IValueName As Variant, Optional ISetValue As String) As String

    On Error GoTo ErrLabel

    Dim lngFindWn As Long
   
    lngFindWn = FindWindow("IEFrame", vbNullString)
    lngFindWn = FindWindowEx(lngFindWn, 0, "shell docobject view", vbNullString)
    lngFindWn = FindWindowEx(lngFindWn, 0, "Internet Explorer_Server", vbNullString)
   
    Set HtmlDoc = Generate(lngFindWn)
   
    Select Case IQuery
        Case 0
        Add_Get = HtmlDoc.documentElement.All(IValueName).Value
        Case 1
        MsgBox (HtmlDoc.nameProp)
       
        HtmlDoc.documentElement.All(IValueName).Value = ISetValue
    End Select
   
    Set HtmlDoc = Nothing
   
ErrLabel:
  Err.Clear
  Exit Function
  Resume
End Function