Calling javascript from within the code behind does not work

This is my role:

<script type="text/javascript">
        function montaDataSubstituicaoPrestador(dt_exclusao) {

            var arrData = dt_exclusao.split('/');
            var exclusaoFormatada = arrData[1] + '-' + arrData[0] + '-' + arrData[2];
            var dias = parseInt(prazoSubPrestador);
            var novaData = new Date(arrData[2], arrData[1] - 1, arrData[0]);

            novaData.setDate(novaData.getDate() + dias);

            hoje = new Date(novaData)
            dia = hoje.getDate()
            mes = hoje.getMonth()
            ano = hoje.getFullYear()
            if (dia < 10)
                dia = "0" + dia

            if ((mes + 1) < 10)
                mes = "0" + (mes + 1);

            if (ano < 2000)
                ano = "19" + ano

            var dt = dia + "/" + (mes) + "/" + ano;

            document.getElementById('lblPrazoSubsAns').innerHTML = "Prazo de substituição: " + dt;
        }
    </script>

And this is my call:

ClientScriptManager cs = Page.ClientScript;
cs.RegisterClientScriptBlock(this.GetType(), "MontaDataExclusaoPrazoANS", "montaDataSubstituicaoPrestador(calDataExclusao.Date)", true);

What happens is that nothing goes up, the label does not change. The function works, but not this way. I tried calling directly in aspx, but it did not work. Below my aspx and I do not know where to call. Just the combo code to call the function.

<table width="100%">
                    <tr>
                        <td style="width:30%; text-align:right">Motivo:</td>
                        <td style="width:70%"><asp:DropDownList ID="ddlMotivoExclusao" runat="server" Width="400px" OnSelectedIndexChanged="ddlMotivoExclusao_OnSelectedIndexChanged" AutoPostBack="true"></asp:DropDownList></td>
                    </tr>
                    <tr id="trDataNotificacaoExclusaoVoluntaria" runat="server" visible="false">
                        <td style="text-align:right">Data Notificação da Exclusão Voluntária:<span style="color:Red">*</span></td>
                        <td><cc1:Calendario id="calDataNotificacaoExclusaoVoluntaria" runat="server" AutoPostBack="false" /></td>
                    </tr>
                    <tr>
                        <td style="text-align:right">Data Exclusão:</td>
                        <td>
                            <cc1:Calendario id="calDataExclusao" runat="server" AutoPostBack="true" OnTextChanged="calDataExclusao_TextChanged" />
                            <asp:Label runat="server" ID="lblPrazoSubsAns">Teste:</asp:Label>
                            <asp:HiddenField ID="hidQtdeDiasExclusao" runat="server" />
                            <asp:HiddenField ID="hidIndLEI13003" runat="server" />
                        </td>
......