Making Menu Item visible or not visible in master page

I have five menu items that i have created as a user control and placed on the master page. Now i want one of the menu items to be visible only for particular user role and not visible for others. Here is what I did. Its not working though. Please suggest how should i go about it. Thanks!!!
Dim DST As New DataSet
DST = dataObject.RunSPReturnDataSet(“uspUserProfile '” & Session(“UserID”).ToString & “'”, “mytbl”)
‘Dim US As New DataSet
‘US = dataObject.RunSPReturnDataSet("uspUserProfile’" & Session(“UserName”).ToString & "’", “mytbl”)
If DST.Tables(0).Rows.Count > 0 Then
Dim MyMasterMenu As Web.UI.Page = Master.FindControl(“NavigationMenu1”)
If Session(“UserID”).ToString = DST.Tables(0).Rows(0).Item(“UserName”).ToString Then
’ And then you can access individual menu items
MyMasterMenu.Items(1).Visible = True
Else
MyMasterMenu.Items(1).Visible = False
End If
End If

You really should be using a SiteMapProvider. SiteMapProviders can centrally describe the site structure of your site and menus etc. can read the site structure from them. SMPs also support “security trimming” which will allow your site to <i>automatically</i> trim the entire structure based on user roles.