Gostaria de pegar o valor do campo "item_valor_total" do formulário pai x filho, tentei por meio da hAPI.getCardValue, mas o valor só vem null.

Alguém saberia ajudar?

<div class="col-md-12">
    <table    tablename="tabelaDeItens"
            id="tabelaDeItens"                                                     
            noaddbutton="true"
            nodeletebutton="true"
            class="tableGrid ecm_tabela"
            style="width:100%" 
            >
        <thead style="font-size:10pt">
            <tr>
                <td class="col-md-2">&nbsp;</td>
                <td class="col-md-4">Centro Custo<font size="4" color="red">*</font></td>
                <td class="col-md-2">Classe Valor</td>
                <td class="col-md-2">Item Contabil</td>
                <td class="col-md-2">Valor</td>
            </tr>
        </thead>
        <tbody class="tabela">
            <tr>
                <td>
                    <button style="cursor:pointer; background-color:#B75555" type="button" class="btn btn-primary btn-md" id="btn_exclui_Item" 
                        onclick="fnCustomDelete(this);" ><font face="verdana" size="1" color="black">Excluir esta Linha</font>
                    </button>
                </td>
                <td>
                    <div class="input-group">
                        <input type="text" class="form-control" name="item_ccusto" id="item_ccusto">
                        <span class="input-group-addon">
                            <a class="fluigicon fluigicon-search fs-cursor-pointer" id="lupa_centro_custo" href="#" class="zoomResponsible" data-select-user="" onClick="Javascript:zoomCentroCusto(this)"></a>
                        </span>
                    </div>
                </td>
                <td>
                    <div class="input-group">
                        <input type="text" class="form-control" name="item_classevalor" id="item_classevalor">
                        <span class="input-group-addon">
                            <a class="fluigicon fluigicon-search fs-cursor-pointer" id="lupa_centro_custo" href="#" class="zoomResponsible" data-select-user="" onClick="Javascript:zoomClasseValor(this)"></a>
                        </span>
                    </div>
                </td>
                <td>
                    <div class="input-group">
                        <input type="text" class="form-control" name="item_itemcontabil" id="item_itemcontabil">
                        <span class="input-group-addon">
                            <a class="fluigicon fluigicon-search fs-cursor-pointer" id="lupa_centro_custo" href="#" class="zoomResponsible" data-select-user="" onClick="Javascript:zoomItemContabil(this)"></a>
                        </span>
                    </div>
                </td>
                <td>
                    <input type="text" class="form-control" name="item_valor" id="item_valor" onKeyPress="return(MascaraMoeda(this,'.',',',event));" onBlur="somarPaiFilho(this);">
                </td>                                    
            </tr>
        </tbody>
        <tfoot>
            <tr valign="bottom">
                <td align="right">&nbsp;</td>
                <td align="right">&nbsp;</td>
                <td align="right">&nbsp;</td>
                <td align="right"><font face="arial" size="2" color="black"><b>Total</b></font></td>
                <td>
                    <input style="font-size:110%;" type="text" class="form-control" name="item_valor_total" id="item_valor_total" readonly>
                </td>                                    
            </tr>
        </tfoot>
    </table>
</div>

var item_valor_total = hAPI.getCardValue("item_valor_total");

2019-11-11 10:46:13,619 INFO  [com.datasul.technology.webdesk.customization.ScriptingLog] (default task-38) ### SP#mec_aprovador#item_valor_total: null