Help with paging and repeaters

I have two repeaters on my page. One for displaying data from a database and the other for holding pagenumbers as linkbuttons which allow navigation through the data.

This seems to work fine. However, I also have three combo boxes which control how the data is sorted. When the combo box is changed I call the DataLoad method which should refresh the PagedDataSource with the new sort details.

However, it doesnt work unless you click on a page number at which point it updates.

www.anon.co.uk/?cat=Music

As you can see, moving around pages works but if you change the combo boxes - nothing happens until you click on a page number.

The code I am using:

using System;
using System.Data;
using System.Collections;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;

public partial class Pieces : System.Web.UI.Page
{
    public int PageNumber
    {
        get
        {
            if (ViewState["PageNumber"] != null)
                return Convert.ToInt32(ViewState["PageNumber"]);
            else
                return 0;
        }
        set
        {
            ViewState["PageNumber"] = value;
        }
    }

    protected override void OnInit(EventArgs e)
    {
        base.OnInit(e);
        rptPages.ItemCommand +=
           new RepeaterCommandEventHandler(rptPages_ItemCommand);
    }

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            string check = Request.QueryString["cat"];
            if (check != null)
            {
                LoadDataCat();

            }
          
        }

    }

    private void LoadDataCat()
    {
        string cat = Request.QueryString["cat"];

        if (cat != null)
        {

           
            cat.Trim();
            cat.Replace("'", "''");
           
            System.Configuration.Configuration rootWebConfig = System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration("/test");
            System.Configuration.ConnectionStringSettings connString;
            connString = rootWebConfig.ConnectionStrings.ConnectionStrings["ConnectionString"];

            SqlConnection cn = new SqlConnection(connString.ConnectionString);
            cn.Open();
            SqlDataAdapter da = new SqlDataAdapter("CatSearch", cn);
            da.SelectCommand.CommandType = CommandType.StoredProcedure;
            da.SelectCommand.Parameters.Add(new SqlParameter("@cat", SqlDbType.VarChar, 40));
            da.SelectCommand.Parameters["@cat"].Value = cat;
            da.SelectCommand.Parameters.Add(new SqlParameter("@RowCount", SqlDbType.Int, 4));
            da.SelectCommand.Parameters["@RowCount"].Direction = ParameterDirection.Output;
            DataTable dt = new DataTable();
            da.Fill(dt);

            cn.Close();

            PagedDataSource pgitems = new PagedDataSource();
            DataView dv = new DataView(dt);
            dv.Sort = getSort();
            pgitems.DataSource = dv;

            pgitems.AllowPaging = true;
            pgitems.PageSize = Convert.ToInt32(DropDownList3.Text);
            pgitems.CurrentPageIndex = PageNumber;

            if (!pgitems.IsLastPage)
            {
                Label2.Text = "Displaying items " + ((pgitems.PageSize * (PageNumber + 1)) - (pgitems.PageSize - 1)) + " - " + (pgitems.PageSize * (PageNumber + 1)) + " from " + da.SelectCommand.Parameters[1].Value;
            }
            else
            {
                Label2.Text = "Displaying items " + ((pgitems.PageSize * (PageNumber + 1)) - (pgitems.PageSize - 1)) + " - " + da.SelectCommand.Parameters[1].Value + " from " + da.SelectCommand.Parameters[1].Value;
            }

            if (pgitems.PageCount > 1)
            {
                rptPages.Visible = true;
                ArrayList pages = new ArrayList();
                for (int i = 0; i < pgitems.PageCount; i++)
                    pages.Add((i + 1).ToString());
                rptPages.DataSource = pages;
                rptPages.DataBind();

            }
            else

                rptPages.Visible = false;
            PageNumber = 0;

            rptItems.DataSource = pgitems;
            rptItems.DataBind();
        }
    }

   
    void rptPages_ItemCommand(object source,
                              RepeaterCommandEventArgs e)
    {
        PageNumber = Convert.ToInt32(e.CommandArgument) - 1;
        string check = Request.QueryString["cat"];
        if (check != null)
        {
            LoadDataCat();
        }
      
    }

    string getSort()
    {
        string sort = "fundraiserReserve ASC";
        switch (DropDownList1.Text)
        {
            case "Name":
                sort = "artistName";
                break;
            case "Fundraisers Reserve":
                sort = "fundraiserReserve";
                break;
            case "Normal Retail Price":
                sort = "retailPrice";
                break;
        }
        switch (DropDownList2.Text)
        {
            case "Ascending":
                sort += " ASC";
                break;
            case "Descending":
                sort += " DESC";
                break;
        }
        return sort;
    }


    protected void DropDownList3_SelectedIndexChanged(object sender, EventArgs e)
    {
        string check = Request.QueryString["cat"];
        if (check != null)
        {
            LoadDataCat();
        }
          
    }
    protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
    {
       string check = Request.QueryString["cat"];
        if (check != null)
        {
            LoadDataCat();
        }
       
    }
    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
       string check = Request.QueryString["cat"];
        if (check != null)
        {
            LoadDataCat();
        }
               }
    }
}

Any help would really be appreciated. Thanks!