Datgrid with paging

I am very new to ASP.net programming and have the last couple of days been lost in a datagrid+paging problem.
I am abel to list the first 5 paged records from the database, but when I press the Next link on the datagrid, everything disappears.
No error message or no new list of records.
Could someone be kind enough to take a look at my code, and point me in the right direction??

The code:

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        If Not IsPostBack Then
            dbGrid.DataSource = bindData()
            dbGrid.DataBind()
        End If

End Sub

Private Sub ImageButton1_Click(ByVal sender As System.Object, ByVal e As System.Web.UI.ImageClickEventArgs) Handles ImageButton1.Click
        bindData()
End Sub

Function bindData() As ICollection
   Dim myConnection As SqlConnection
   Dim myCommand As SqlDataAdapter
   myConnection = New SqlConnection("server=xxxxxxx;uid=xxxx;pwd=xxxxx;database=xxxxx;")
   myCommand = New SqlDataAdapter("SELECT var1,var2,3,var4,var5 FROM Table1", myConnection)

   Dim ds As DataSet = New DataSet()
   myCommand.Fill(ds)
   dbGrid.DataSource = ds
   dbGrid.DataBind()
End Function

Sub dbGrid_PageIndexChanged(ByVal source As Object, ByVal e As System.Web.UI.WebControls.DataGridPageChangedEventArgs) Handles dbGrid.PageIndexChanged
   dbGrid.CurrentPageIndex = e.NewPageIndex
   dbGrid.DataSource = bindData()
   dbGrid.DataBind()
End Sub