You access an IServers object by calling the IBuildServer.Sites property, as in the following example, where objServers is the name you give to the IServers object:
Option Explicit
On Error Resume Next
Dim objSearchAdmin, objBuildServer, objServers
Set objSearchAdmin = CreateObject("Search.SearchAdmin.1")
Set objBuildServer = objSearchAdmin.BuildServer
Set objServers = objBuildServer.Sites
...
'Release objects
Set objServers = Nothing
Set objBuildServer = Nothing
Set objSearchAdmin = Nothing