In all of the later versions (at least since 2009) it is included:

Place the data in three columns:

       x | y | bubble size 

select this table and choose:

       Insert -> Diagram -> Bubble Diagram

In the properties of the diagram, further series can be added.

Thank you Mr. Olof Dahlberg  for your prompt information. Really appreciate it. but what i need to do is to place these bubbles in a map to provide the viewer with an idea of the relevant location as well 

NuwanAdd your answer

This can be easily done in R. Bubble graphs can be plot in Excel but not maps. So you have to move software capable of both GIS and plots.  

http://www.molecularecologist.com/2012/09/making-maps-with-r/

Changing the background in the diagram is also available.

Scaling of the axes should enable you to position your points, as long as some reference can be found, otherwise edit your map image to match up with your map coordinates, or transform your map coordinates to match the projection of the map.

Thanks Mr. Dahlberg, I'll try that as well.