urg-how to sort datagrid having calculated column

[samir]

hi
i have a datagrid where i display some columns. i want to have some
columns from the db and 2 i calculate,i can display it but problem is
how to sort the calculated columns.
here is what i am doing right now:

on page load i have:
If Not Me.IsPostBack Then
strSQL = "select FILEID, FILENAME,
APPSERVICETYPE,LOCATION,FILEREPORT, DESCRIPTION, location2 FROM
DOWNLOADFILES WHERE (@lower(ORGANISATION)=@lower('" & Orgn & "') or
@lower(ORGANISATION)='dfe') and FILEREPORT='REPORT' order by
APPSERVICETYPE, FILENAME "
bindGrid()
End If


and in bindgrid i have :
GoToDBOpenConn()
bjCommand = New OleDbCommand(strSQL, objConnection)
myDa.SelectCommand = objCommand
Dim dt As New DataTable
myDa.Fill(dt)
Me.dgFiles.DataSource = dt
Me.dgFiles.DataBind()

in itemdatabound i calculate the columns
Private Sub dgFiles_ItemDataBound(ByVal sender As Object, ByVal e As
System.Web.UI.WebControls.DataGridItemEventArgs) Handles
dgFiles.ItemDataBound

If e.Item.ItemType =
System.Web.UI.WebControls.ListItemType.AlternatingItem Or
e.Item.ItemType = System.Web.UI.WebControls.ListItemType.Item Or
e.Item.ItemType = System.Web.UI.WebControls.ListItemType.EditItem Then
Dim lbl, lbl2 As System.Web.UI.WebControls.Label
Dim row As DataRowView = CType(e.Item.DataItem,
DataRowView)
lbl = e.Item.FindControl("lblSize")
lbl2 = e.Item.FindControl("lblMdDate")
Dim phyPath As String
phyPath =
Server.MapPath(ByteArrayToString(row("LOCATION")))

e.Item.Cells(2).Text = phyPath
FilePath = e.Item.Cells(2).Text
filename = e.Item.Cells(3).Text
Dim fi As FileInfo = New FileInfo(FilePath & filename)
Dim fileBytes As Integer = (fi.Length / 1024)
Dim lastmodifeddt As Date =
File.GetLastWriteTime(FilePath & filename)
lastmodifeddt = lastmodifeddt.Date
lbl.Text = fileBytes.ToString
lbl2.Text = lastmodifeddt

Dim urlParams As String = "FileID=" +
row("FILEID").ToString()
Dim tabid As Int32 = 185 'row("TABID1")
e.Item.Cells(4).Text = "<A href='" &
DotNetNuke.Common.Globals.NavigateURL(tabid, "", urlParams) & "'
target=""_parent"">" + ByteArrayToString(row("DESCRIPTION")) & "</A>"

End If
End Sub

now when i sort right i am having:
Sub SortCommand_OnClick(ByVal Source As Object, ByVal E As
System.Web.UI.WebControls.DataGridSortCommandEventArgs)
strSQL = "select FILEID, FILENAME,
APPSERVICETYPE,LOCATION,FILEREPORT, DESCRIPTION, location2 FROM
DOWNLOADFILES WHERE (@lower(ORGANISATION)=@lower('" & Orgn & "') or
@lower(ORGANISATION)='dfe') and FILEREPORT='REPORT' ORDER BY " &
E.SortExpression()
GetDeptOfUserLogged()
bindGrid()
End Sub

but here if i sort the caluclated columns then that column doesnt exists
in db? how can this issue be resolved. can anyone help on this?
thanks a lot