Dim strFile     As String
Dim strFilter   As String

On Error GoTo Err_cmdOpen_Click

    ' Узнать у пользователя путь к файлу
    strFilter = "Все поддерживаемые файлы(*.adtg,*.rar)|*.adtg;*.rar|" _
            & "ADTG-формат (*.adtg)|*.adtg|" _
            & "RAR-архив (*.rar)|*.rar||"
    strFile = Get_File_Name(Me.hWnd, "Открыть файл...", CurrentProject.Path, strFilter)
    If Len(strFile) >  0  Then
        If Right$(strFile,  4 ) = ".rar" Or Right$(strFile,  5 ) = ".adtg" Then
            ... обработка файла
        Else
            MsgBox "Извините, поддерживаются только форматы ADTG и RAR!", vbExclamation, "Неизвестный формат"
        End If
    End If

Exit_cmdOpen_Click:

    Exit Sub

Err_cmdOpen_Click:
    ufErrorNotification "cmdOpen_Click"
    Resume Exit_cmdOpen_Click
    

Option Compare Database
Option Explicit

Type OPENFILENAME
        lStructSize As Long
        hWndOwner As Long
        hInstance As Long
        lpstrFilter As String
        lpstrCustomFilter As String
        nMaxCustFilter As Long
        nFilterIndex As Long
        lpstrFile As String
        nMaxFile As Long
        lpstrFileTitle As String
        nMaxFileTitle As Long
        lpstrInitialDir As String
        lpstrTitle As String
        flags As Long
        nFileOffset As Integer
        nFileExtension As Integer
        lpstrDefExt As String
        lCustData As Long
        lpfnHook As Long
        lpTemplateName As String
End Type

Declare Function GetOpenFileName Lib "comdlg32.dll" Alias "GetOpenFileNameA" (pOpenfilename As OPENFILENAME) As Long

Declare Function GetSaveFileName Lib "comdlg32.dll" Alias "GetSaveFileNameA" (pOpenfilename As OPENFILENAME) As Long

Declare Function GetFileTitle Lib "comdlg32.dll" Alias "GetFileTitleA" (ByVal lpszFile As String, ByVal lpszTitle As String, ByVal cbBuf As Integer) As Integer

Public Const OFN_READONLY = &H1
Public Const OFN_OVERWRITEPROMPT = &H2
Public Const OFN_HIDEREADONLY = &H4
Public Const OFN_NOCHANGEDIR = &H8
Public Const OFN_SHOWHELP = &H10
Public Const OFN_ENABLEHOOK = &H20
Public Const OFN_ENABLETEMPLATE = &H40
Public Const OFN_ENABLETEMPLATEHANDLE = &H80
Public Const OFN_NOVALIDATE = &H100
Public Const OFN_ALLOWMULTISELECT = &H200
Public Const OFN_EXTENSIONDIFFERENT = &H400
Public Const OFN_PATHMUSTEXIST = &H800
Public Const OFN_FILEMUSTEXIST = &H1000
Public Const OFN_CREATEPROMPT = &H2000
Public Const OFN_SHAREAWARE = &H4000
Public Const OFN_NOREADONLYRETURN = &H8000
Public Const OFN_NOTESTFILECREATE = &H10000
Public Const OFN_NONETWORKBUTTON = &H20000
Public Const OFN_NOLONGNAMES = &H40000
Public Const OFN_EXPLORER = &H80000    'new look commdlg
Public Const OFN_NODEREFERENCELINKS = &H100000
Public Const OFN_LONGNAMES = &H200000  'force long names for 3.x modules

Public Const OFN_SHAREFALLTHROUGH =  2 
Public Const OFN_SHARENOWARN =  1 
Public Const OFN_SHAREWARN =  0 

Public Function Get_File_Name(hWnd As Long, _
                              title As String, _
                              Path As String, _
                              txt_filter As String) As String
  Get_File_Name = Get_File_NameCommon(hWnd, title, Path, "", "", txt_filter, True)
  
End Function

Public Function Get_File_NameCommon(hWnd As Long, _
                                    title As String, _
                                    Path As String, _
                                    Ftitle As String, _
                                    fext As String, _
                                    txt_filter As String, _
                                    saveflag As Boolean) As String
Dim ofn As OPENFILENAME
Dim ret As Long
Dim fn As String *  129 , fp As String *  129 
Dim s As String, i As Integer
' On Error GoTo errfnm
    
    Get_File_NameCommon = ""
    
    txt_filter = Replace(txt_filter, "|", Chr( 0 ))
    
    If Len(Ftitle) <>  0  Then fn = Ftitle + Chr( 0 )
    With ofn
        .lStructSize =  76 
        .hWndOwner = hWnd
        'ofn.hInstance = 0
        .lpstrFilter = txt_filter
        .lpstrCustomFilter =  0 
        .nMaxCustFilter =  0 
        .nFilterIndex =  1 
        .lpstrFile = fn
        .nMaxFile =  128 
        .lpstrFileTitle = fp
        .nMaxFileTitle =  128 
        .lpstrInitialDir = Path
        .lpstrTitle = title
    End With
    If Len(fext) <>  0  Then ofn.lpstrDefExt = fext
    If Not saveflag Then
        ofn.flags = OFN_PATHMUSTEXIST + _
                    OFN_FILEMUSTEXIST + _
                    OFN_NOLONGNAMES + _
                    OFN_EXPLORER +  0 
        ret = GetOpenFileName(ofn)
    Else
        ofn.flags = OFN_PATHMUSTEXIST + _
                    OFN_NOLONGNAMES + _
                    OFN_EXPLORER +  0 
        ret = GetSaveFileName(ofn)
    End If
    'ofn.nFileOffset = 0
    'ofn.nFileExtension = 0
    'ofn.lCustData = 0
    'ofn.lpfnHook = 0
    'ofn.lpTemplateName = 0
    
    Get_File_NameCommon = ""
    If ret <>  0  Then
        For i =  1  To  129 
            s = Mid$(ofn.lpstrFile, i,  1 )
            If Asc(s) =  0  Or Len(s) =  0  Then Exit For
            Get_File_NameCommon = Get_File_NameCommon & s
        Next
    End If
exitfnm:
    Exit Function
errfnm:
    MsgBox Err.Description
    Get_File_NameCommon = ""
    Resume exitfnm
End Function