How gan I access Google PageRank Parameter from an external
Application...Does Google ToolBar has an OLE automation engine or
ActiveX....

The google toolbar is an exmample of a custom IE toolbar. If you are
interested, this article explains how to write one:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/shellcc/platform/Shell/programmersguide/shell_adv/bands.asp

My guess is that it is not easy to manipulate this object
programatically. However, it should be possible to request the
PageRank value directly from google.com (this is after all exactly
what their toolbar does every time you hit a web page).

This article should give you everything you need to recreate the
PageRank HTTP request.
http://www.httprevealer.com/usage_google.htm

Also see:
http://pr.efactory.de/e-pagerank-implementation.shtml

Hope this helps. Richard McGrath