B4J Question Updating a TextArea while running a long computation

Private Sub WriteLog(line As String)
    Logger.WriteDebugLog("MAIN: " & line)
    
    If (TextArea1.IsInitialized) Then
        UpdateTextArea
    End If
End Sub

Private Sub UpdateTextArea
    TextArea1.Text = Logger.GetBuffer
    TextArea1.SetSelection(TextArea1.Text.Length, TextArea1.Text.Length)
    Sleep(0)
End Sub

Private Sub SplitLongLog
    Dim dir As String = Preferences.GetString(Preferences.OPT_DIR)
    Dim filename As String = Preferences.GetString(Preferences.OPT_FILENAME)
    Dim linenumber As Int = 0

    WriteLog($"Split ${dir}\${filename}"$)
    
    Private inTextFile As TextReader
    
    Try
        inTextFile.Initialize(File.OpenInput(dir, filename))
    
        Dim line As String = ""
        Do While line <> Null
            line = inTextFile.ReadLine
            
            If (line <> Null) Then
                linenumber = linenumber + 1
                If (linenumber Mod 1000) = 0 Then
                    WriteLog("processing line " & linenumber)
                End If
                
                If Regex.IsMatch(pattern, line) Then
                    'process the line
                    'time consuming
                End If
            End If
        Loop
    Catch
        Log(LastException)
    End Try

    If (inTextFile.IsInitialized) Then
        inTextFile.Close
    End If
End Sub