what i m trying is i hav two dropdownlists inside the gridview... namely say ddonsiteoffsite and ddhours... now what i want is if the selectedtext of ddonsiteoffsite is "onsite" the ddhours should b disabled... i tried the code snippet but ... its not disabling the ddhours... can someone help me please..

<asp:TemplateColumn HeaderText="      OnSite/OffSite" >   
                <ItemTemplate>   
                     <asp:DropDownList ID="ddOnsiteOffside" runat="server" onchange="ToggleOnOff(this)"><asp:ListItem Text = "Offsite" Value="Offsite"></asp:ListItem>        
                        <asp:ListItem Text = "Onsite" Value="Onsite"></asp:ListItem> 
                      </asp:DropDownList>   
                </ItemTemplate>   
            </asp:TemplateColumn>   
             <asp:TemplateColumn>   
                <ItemTemplate>   
                    <asp:DropDownList ID="ddhours" runat="server">   
                        <asp:ListItem Text = "1" Value="1" ></asp:ListItem>   
                        <asp:ListItem Text = "2" Value="2" ></asp:ListItem>   
                        <asp:ListItem Text = "3" Value="3" ></asp:ListItem>   
                        <asp:ListItem Text = "4" Value="4" ></asp:ListItem>   
                        <asp:ListItem Text = "5" Value="5" ></asp:ListItem>   
                        <asp:ListItem Text = "6" Value="6" ></asp:ListItem>   
                        <asp:ListItem Text = "7" Value="7" ></asp:ListItem>   
                        <asp:ListItem Text = "8" Value="8" ></asp:ListItem>   
                        <asp:ListItem Text = "9" Value="9" ></asp:ListItem>   
                    </asp:DropDownList>   
                </ItemTemplate>   
            </asp:TemplateColumn>

and the corresponding javascript i am using is :

enter code here

function ToggleOnOff(ddonoff)
{

     var row = chk.parentNode.parentNode;              
     if(ddonoff.value=="Onsite")    
     {           
          row.getElementsByTagName("ddhours")[0].disabled = true;                   
     }   
     else   
          row.getElementsByTagName("ddhours")[0].disabled = false;                    
 } 

can someone help to achieve this ?? using javascript or jquery ? i m not understanding where i went wrong ...