how to call code behind method inside the datalist aspx page

//Code Behind
 public string GetTimerem( object pd)
    {
        DateTime d1 = Convert.ToDateTime(pd), d2 = DateTime.Now;
        int d3, t3;
        d3 = d2.Subtract(d1).Days;
        t3 = d2.Subtract(d1).Hours;
       // Label l1 = (Label)dlAdsList.Controls[0].FindControl("lblBuyTimeRem");

        string timeRem = d3.ToString() + " Days " + t3.ToString() + "  Hrs";
        return timeRem;    //l1.Text = "df";
        //Label1.Text = d3.ToString() + " Days " + t3.ToString() + "  Hrs";
        //  dtl.Text= _objDataTableAdsInfo.Rows[0]["PostDate"].ToString();

    }

//aspx page
<asp:DataList id ="dlAdsList" runat ="server" >
<  <ItemTemplate>
 <asp:Label ID="lblTimeVRemainingAuction" runat="server" Text='<%# GetTimerem(DataBinder.Eval(Container.DataItem,"PostDate")) %>'></asp:Label>
</ItemTemplate>
</datalist>