Radio button +Textbox Custom validations

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C#

ASP.NET

hai i have

one simple radio buttion list like this

<td>
                            <asp:RadioButtonList ID="rb_Question1" runat="server" ValidationGroup="req" Height="16px"
                                RepeatColumns="2" Width="220px"    >
                                <asp:ListItem Text="Yes" Value="1"></asp:ListItem>
                                <asp:ListItem Text="No" Value="0"></asp:ListItem>
                            </asp:RadioButtonList>
                        </td>

when user click on the No button based on no button Textbox comments will be required

my textbox is as follows

<tr>
                        <td align="right"><b>Comments:</b></td>
                        <td colspan="2" class="row">
                            <div class='textAreaDiv'>
                                <asp:TextBox ID="ReviewerDecsion_txt" class="border" runat="server" TextMode="MultiLine" Width="800px" Height="120px"></asp:TextBox>
                                <asp:CustomValidator ID="cv_ReviewerDecsion_txt" runat="server"  ValidateEmptyText="true"

                                ClientValidationFunction="ReviewerDecsiontxt" ErrorMessage="Enter text for Approve this applicant to become a surveyor?"
                                ForeColor="Red" Text="*"  ValidationGroup="req"></asp:CustomValidator>
                            </div>
                        </td>

i WANT cUSTOMER Validation for this


my scirpt is as follows it is not working

function ReviewerDecsiontxt(sender, args) {
            var radbtn1 = $("#cphMaster_rb_Question1_0");
            var radbtn2 = $("#cphMaster_rb_Question1_1");
            var ReviewerTxtbox = $("#ReviewerDecsion_txt");
            if ((radbtn1[0].checked ) &&(ReviewerTxtbox.text)!= "")
            { args.IsValid = true; }
            else { args.IsValid = false; }

               }