Option Explicit

Private Declare PtrSafe Function FindWindowEx Lib "user32" Alias "FindWindowExA" (ByVal hWndParent As Long, ByVal hwndChildAfter As Long, ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare PtrSafe Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare PtrSafe Function GetWindowText Lib "user32" Alias "GetWindowTextA" (ByVal hwnd As Long, ByVal lpString As String, ByVal cch As Long) As Long
Private Declare PtrSafe Function GetWindowTextLength Lib "user32" Alias "GetWindowTextLengthA" (ByVal hwnd As Long) As Long
Private Declare PtrSafe Function IsWindowVisible Lib "user32" (ByVal hwnd As Long) As Boolean
Private Declare PtrSafe Function PostMessageW Lib "user32" (ByVal hwnd As Long, ByVal Msg As Long, ByVal wParam As Integer, ByVal lParam As Integer) As Boolean
Private Declare PtrSafe Function GetWindow Lib "user32" (ByVal hwnd As Long, ByVal wCmd As Long) As Long

Private Const GW_HWNDNEXT = 2
Private Const WM_KEYDOWN As Integer = &H100
Private Const VK_Enter = &HD
Private Const VK_ESCAPE = &H3

Sub myPressButton()
    Dim lhWndP As Long
    If GetHandleFromPartialCaption(lhWndP) = True Then
        'If IsWindowVisible(lhWndP) = True Then
        'End If
    End If
End Sub

Private Function GetHandleFromPartialCaption(ByRef lWnd As Long) As Boolean
    Const windowCaption = "Тест1"
    Const buttonCaption = "Кнопка1"
    
    Dim hwndButt As Long
    Dim lhWndP As Long
    Dim sStr As String
    GetHandleFromPartialCaption = False
    lhWndP = FindWindow(vbNullString, vbNullString) 'PARENT WINDOW
    Do While lhWndP <> 0
        sStr = String(GetWindowTextLength(lhWndP) + 1, Chr$(0))
        GetWindowText lhWndP, sStr, Len(sStr)
        sStr = Left$(sStr, Len(sStr) - 1)
        If InStr(1, sStr, windowCaption) > 0 Then
            GetHandleFromPartialCaption = True
            lWnd = lhWndP
            hwndButt = FindWindowEx(lhWndP, ByVal 0&, vbNullString, buttonCaption)
            PostMessageW hwndButt, WM_KEYDOWN, VK_Enter, 0
        End If
        lhWndP = GetWindow(lhWndP, GW_HWNDNEXT)
    Loop
End Function

PostMessageW hwndButt, WM_KEYDOWN, VK_Enter, 0

Debug.Print FindWindowEx(FindWindow(vbNullString, "Тест1"), 0, vbNullString, "Отмена")

Debug.Print FindWindow(vbNullString, "Тест1")

Debug.Print FindWindowEx(FindWindow(vbNullString, "Тест1"), 0, vbNullString, "Отмена")

Debug.Print FindWindowEx(FindWindow("TfrmRadioSel", "Тест1"), 0, vbNullString, "Отмена")

    Dim hwnd As Long
    hwnd = FindWindow("TfrmRadioSel", "Тест1")
    If hwnd <> 0 Then
        Debug.Print "Parent window hwnd: " & hwnd
        hwnd = FindWindowEx(hwnd, 0, vbNullString, "Отмена")
        Debug.Print "Button window: " & hwnd
    End If