How to validate asp textbox in side gridview

I am trying to validate asp textbox inside grid-view but my challenge is that i have 3 item templates in my aspx page,
ID
Question
Answer
The questions are generated dynamically after the grid view.bind() is called but i want to put some validation on the Answer field where users have to enter specific answer only based on the ID.  For example, If ID = 1 then they can only enter age number like 1 to 99. If ID = 2 then they can only enter some kind height values like 5.3, 5.8 etc. Here is how my current grid view look like

<asp:GridView ID="GV_Test" runat="server"  
                    AutoGenerateColumns="False"
                    ShowFooter="True" DataKeyNames="ID">
                    <Columns>

                        <asp:TemplateField  HeaderText="Question ID" Visible="true">
                            <ItemTemplate>
                                <asp:Label ID="lblQST_SK" runat="server" Text='<%# Eval("ID")%>'></asp:Label>
                            </ItemTemplate>
                        </asp:TemplateField>


                        <asp:TemplateField ItemStyle-Width="150px" HeaderText="Questions">
                            <ItemTemplate>
                                <asp:Label ID="lblQuestions" runat="server" Text='<%# Eval("Question")%>'></asp:Label>
                            </ItemTemplate>                                
                        </asp:TemplateField>

                        <asp:TemplateField HeaderText="Answer">                              
                                <ItemTemplate>                               
                                  <asp:TextBox ID="txtAn" runat="server" CssClass="form-control" Text='<%# Eval("Answer")%>' ></asp:TextBox>
                            </ItemTemplate>
                        </asp:TemplateField>

                    </Columns>

                </asp:GridView>

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I believe i have to use some kind of javascript that uses some kind event like onkeyup or onclick() something like this but not sure how to use it.   Please help.   thanks