Gridview, recordset and paging for Grid - Please help

I am assigning a daset of records to  a girdview object
want to be able to do paging in my code
here is code I have 
I am confussed with th pageindex


I thought that when I click on the page mnuber it will return that number in pageindex and I can use it to calculate next set of data where to start and load the grid and bind it again
 Then would like that page number showing in the grid as current page now

I do it in code since I will eventually biuld the select statemnet based on variables passed in
Code here:
Size if grid is 5 records

Protected Sub GV5_PageIndexChanging(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewPageEventArgs) Handles GV5.PageIndexChanging
        Dim sqlString As String
        Dim con As OracleConnection
        Dim xSt ...