object required error when loop within subfolders in selected row from listbox on userform

[Mussala]

Hi
this is the original code

Private Declare Function [B]apiShellExecute[/B] Lib "shell32.dll" _
 Alias "ShellExecuteA" _
(ByVal hwnd As Long, ByVal lpOperation As String, ByVal lpFile As String, _
ByVal lpParameters As String, ByVal lpDirectory As String, ByVal nShowCmd As Long) As Long

Private Sub ListBox1_Click()
   [B] Dim Filename As String[/B]

    With ListBox1
        'change path to suit
        Filename = "C:\Users\MU\Desktop\pdf Folder\" &[B] .List(.ListIndex, 1)[/B] & ".pdf"
        ' Test if file exists...
        If Dir(Filename) <> vbNullString Then
            '... if so, write column 2 value to text box
            TextBox1 = .List(.ListIndex, 1)
            ' and open pdf
            [B]apiShellExecute[/B] 0, "Open", Filename, "", "", vbMaximizedFocus
            Else
            ' otherwise tell user and stop
            MsgBox "Sorry but the following file was not found:" & vbCr & Filename
            Exit Sub
        End If
    End With


    'ListBox1.ListIndex = -1
End Sub

the code will open pdf file by click selected row from listbox , but my problem the code doesn't deal with files are existed in subfolders within the main folder in the main directory
I try with this

Private Sub ListBox1_Click()
    Dim Filename As String
    Set objFso = CreateObject("Scripting.FileSystemObject")

    With ListBox1
        'change path to suit
        Set ObjFolder = "C:\Users\MU\Desktop\pdf Folder\" & .List(.ListIndex, 1) & ".pdf"
        For Each objSubFile In ObjFolder.Files
        If InStr(objSubFile.Name, ".pdf") > 0 Then
            Debug.Print objSubFile.Path
        End If
    Next objSubFile
    ' call the function to loop through its subfolders (and theirs)
    LoopEachFolder ObjFolder

    ' quit FSO
    Set objFso = Nothing
        ' Test if file exists...
        If Dir(ObjFolder) <> vbNullString Then
            '... if so, write column 2 value to text box
            TextBox1 = .List(.ListIndex, 1)
            ' and open pdf
            apiShellExecute 0, "Open", ObjFolder, "", "", vbMaximizedFocus
            Else
            ' otherwise tell user and stop
            MsgBox "Sorry but the following file was not found:" & vbCr & Filename
            Exit Sub
        End If
    End With
    
    
    'ListBox1.ListIndex = -1
End Sub

Function LoopEachFolder(fldFolder As Object)

    ' With the subfolders in this folder....
    For Each objFldLoop In fldFolder.subFolders
        ' ...loop through files in this folder
        For Each objSubFile In objFldLoop.Files
            If InStr(objSubFile.Name, ".pdf") > 0 Then
                Debug.Print objSubFile.Path
            End If
        Next objSubFile
        ' ... and run the function on each subfolder found
        LoopEachFolder objFldLoop

    Next objFldLoop

End Function

but gives error object required in this line

Set ObjFolder = "C:\Users\MU\Desktop\pdf Folder\" & .List(.ListIndex, 1) & ".pdf"

how can I make this code deals with folders & subfolders when I try open PDF file ?
thanks