URL = "https://b24-ar17wx.bitrix24.by/rest/1/1o2...";

    FieldID = "255";
    Title   = "New title";

    Result = OPI_Bitrix24.UpdateCustomTaskField(URL, FieldID, , Title);

    URL   = "b24-ar17wx.bitrix24.by";
    Token = "6476c766006e9f06006b12e400000001000...";

    FieldID    = "257";
    ExternalID = "NEW_TEXT_FIELD";
    Signature  = New Structure("en,ru", "Updated field", "Izmenennoe pole");

    Result = OPI_Bitrix24.UpdateCustomTaskField(URL, FieldID, ExternalID, , Signature, Token);