How can I convert vba macro with findwindow api into google app script?

Question

I'd like to convert VBA macro to Google Apps script but I think this particular one is impossible to convert as I am totally lost where to begin with this. I couldn't find anyway to do what "findwindow" does on APP script. Does anyone have any idea how to tackle this or should I give up on this?

Plus, is there anyone played with the phone companion? As they don't provide any API, the only way to use the mobile companion to send messages with google spread would be using findwindow, which shows the same problem. Any insight on this would be highly appreciated. Thanks.

Option Explicit

 
#If VBA7 Then
' https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-findwindowa
Private Declare PtrSafe Function FindWindow Lib "user32.dll" Alias "FindWindowA" _
                                                        (ByVal lpClassName As String, _
                                                        ByVal lpWindowName As String) As Long

' https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-findwindowexa
Public Declare PtrSafe Function FindWindowEx Lib "user32.dll" Alias "FindWindowExA" _
                                                            (ByVal hwndParent As Long, _
                                                            ByVal hwndChildAfter As Long, _
                                                            ByVal lpszClass As String, _
                                                            ByVal lpszWindow As String) As Long


' https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-sendmessagea
Private Declare PtrSafe Function SendMessage Lib "user32" Alias "SendMessageA" _
                                                            (ByVal hwnd As Long, _
                                                            ByVal wMsg As Long, _
                                                            ByVal wParam As Long, _
                                                            ByRef lParam As Any) As Long

'https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-postmessagea
Private Declare PtrSafe Function PostMessage Lib "user32" Alias "PostMessageA" _
                                                            (ByVal hwnd As Long, _
                                                            ByVal wMsg As Long, _
                                                            ByVal wParam As Long, _
                                                            ByRef lParam As Any) As Long

Private Declare PtrSafe Function GetNextWindow Lib "user32" Alias "GetWindow" (ByVal hwnd As Long, ByVal wFlag As Long) As Long
Private Declare PtrSafe Sub Sleep Lib "kernel32" (ByVal Milliseconds As LongPtr)

#Else
' https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-findwindowa
Private Declare Function FindWindow Lib "user32.dll" Alias "FindWindowA" _
                                                        (ByVal lpClassName As String, _
                                                        ByVal lpWindowName As String) As Long

' https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-findwindowexa
Public Declare Function FindWindowEx Lib "user32.dll" Alias "FindWindowExA" _
                                                            (ByVal hwndParent As Long, _
                                                            ByVal hwndChildAfter As Long, _
                                                            ByVal lpszClass As String, _
                                                            ByVal lpszWindow As String) As Long
' https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-sendmessagea
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
                                                            (ByVal hwnd As Long, _
                                                            ByVal wMsg As Long, _
                                                            ByVal wParam As Long, _
                                                            ByRef lParam As Any) As Long

'https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-postmessagea
Private Declare Function PostMessage Lib "user32" Alias "PostMessageA" _
                                                            (ByVal hwnd As Long, _
                                                            ByVal wMsg As Long, _
                                                            ByVal wParam As Long, _
                                                            ByRef lParam As Any) As Long

>Private Declare Function GetNextWindow Lib "user32" Alias "GetWindow" (ByVal hwnd As Long, ByVal wFlag As Long) As Long
Private Declare Sub Sleep Lib "kernel32" (ByVal Milliseconds As LongPtr)
#End If

Dim Handle, HandleEx As Long

Private Const WM_SETTEXT = &HC: Private Const WM_KEYDOWN = &H100
Private Const VK_RETURN = &HD:  Private Const VK_ESCAPE = &H1B
Private Const WM_CLOSE = &H10:  Private Const GW_HWNDNEXT = &H2

 
Sub Send_Kakao(Target As Range, Msg As Range)

Dim SendTo$: SendTo = Target.Value
Dim Message$: Message = Msg.Value
 
Dim hwnd_KakaoTalk As Long: Dim hwnd_RichEdit As Long
Call Call_ChatRoom(Target)
DoEvents
Sleep 1000
 
hwnd_KakaoTalk = FindWindow(vbNullString, SendTo)
hwnd_RichEdit = FindWindowEx(hwnd_KakaoTalk, 0, "RichEdit50W", vbNullString)
 
If hwnd_RichEdit = 0 Then MsgBox SendTo & "This chatroom is not opened.": Exit Sub
 
Call SendMessage(hwnd_RichEdit, WM_SETTEXT, 0, ByVal Message)
Call PostMessage(hwnd_RichEdit, WM_KEYDOWN, VK_RETURN, 0)
 
End Sub

Private Sub Call_ChatRoom(Target As Range)
    
    Dim ChatRoom$: ChatRoom = Target.Value
    Dim rtnV As Long
    
    Handle = FindWindow("EVA_Window_Dblclk", vbNullString) 'Saave Window Handle info of Kakao on Handle
    '//Print error when cannot be located
    If Handle = 0 Then
    MsgBox "Open kakao first.", 16, "Error"
    
    Else
        HandleEx = FindWindowEx(Handle, 0, "EVA_ChildWindow", vbNullString)  'children Window1
        HandleEx = FindWindowEx(HandleEx, 0, "EVA_Window", vbNullString)  'children  Window2
        HandleEx = FindWindowEx(HandleEx, 0, "Edit", vbNullString)  'children Window3
    
        Call SendMessage(HandleEx, WM_SETTEXT, 0, ByVal ChatRoom)
        DoEvents
        Sleep 1000
        
        Call PostMessage(HandleEx, WM_KEYDOWN, VK_RETURN, 0)
    End If
    
End Sub