Shell "proga.exe <параметры>", vbHide
                Timer1.Enabled = True 'перезапуск таймера ожидания конца конвертации

Private Sub Timer1_Timer()
        If IsProgaRun("proga") = False Then
            <действия>
            Timer1.Enabled = False
        End If
End Sub

Function IsProgaRun(proga As String) As Boolean
        TargetName = proga
        TargetHwnd = 0
        ' Examine the window names.
        EnumWindows AddressOf WindowEnumerator, 0
        ' See if we got an hwnd.
        If TargetHwnd = 0 Then
            IsProgaRun = False
        Else
            IsProgaRun = True
        End If
End Function
' Return False to stop the enumeration.
Public Function WindowEnumerator(ByVal app_hwnd As Long, _
    ByVal lParam As Long) As Long
Dim buf As String * 256
Dim Title As String
Dim length As Long

    ' Get the window's title.
    length = GetWindowText(app_hwnd, buf, Len(buf))
    Title = Left$(buf, length)

    ' See if the title contains the target.
    If InStr(Title, TargetName) > 0 Then
        ' Save the hwnd and end the enumeration.
        TargetHwnd = app_hwnd
        WindowEnumerator = False
    Else
        ' Continue the enumeration.
        WindowEnumerator = True
    End If
End Function

                Shell "proga.exe <параметры>", vbHide
                Do
                  DoEvents
                  If IsProgaRun("proga") = true then exit do 'проконтролировать запуск процесса
                Loop
                Timer1.Enabled = True 'перезапуск таймера ожидания конца конвертации

                Shell "proga.exe <параметры>", vbHide
                Do
                  DoEvents
                  If IsProgaRun("proga") = true then exit do 'проконтролировать запуск процесса
                Loop
                Timer1.Enabled = True 'перезапуск таймера ожидания конца конвертации

    Dim ltime As Single
...
                Shell "proga.exe ............., vbHide
                ltime = Timer()
                Do
                    DoEvents
                    If (IsProgaRun("proga") = True) Or (Timer - ltime > 1) Or (Timer < ltime) Then
                        Exit Do
                    End If
                Loop
                Timer1.Enabled = True 'перезапуск таймера ожидания конца конвертации

Sub ShellAndContinue(ByVal AppToRun As String, mode As VbAppWinStyle)
   ' On Error GoTo ErrorRoutineErr
    
    Dim hProcess As Long
    Dim retVal As Long
    Dim Msg, Style, Title, Response 'msgbox variables
    
    'The next line launches AppToRun,
    'captures process ID
    hProcess = OpenProcess(PROCESS_QUERY_INFORMATION, 1, _
    Shell(AppToRun, mode))
    Do
        'Get the status of the process
        GetExitCodeProcess hProcess, retVal
        DoEvents
    'Loop while the process is active
    Loop While retVal = STILL_ACTIVE
    
ErrorRoutineResume:
    Exit Sub
'ErrorRoutineErr:
'    MsgBox Error.Description
End Sub

Or (Timer - ltime > 1)

Or (Timer < ltime)