Few ways to do so.
TAJ's Linking PowerPoint Presentations Together Seamlessly:
http://www.awesomebackgrounds.com/powerpointlinking.htm
or, you can try out Invisible Linking:
http://msmvps.com/blogs/tohlz/archive/2007/09/25/invisible-linking.aspx

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Shawn Toh (tohlz)
Microsoft MVP PowerPoint
Site Updated: Oct 20, 2007
(Amazing PowerPoint animations, artworks, games here)
http://pptheaven.mvps.org
PowerPoint Heaven - The Power to Animate
> I would like to show powerpoint slides automatically (during a slide show),
> but, in addition, like to a second (and third) powerpoint sequence at the end
> of the first. Is there a way to link automatically without needed personal
> attention? It can be done with a hyperlink, but that needs a click. Any
> suggestions?
VB_User - 31 Dec 2007 14:54 GMT
Just what I was looking for. Thank you!!!
> Few ways to do so.
> TAJ's Linking PowerPoint Presentations Together Seamlessly:
[quoted text clipped - 8 lines]
> > attention? It can be done with a hyperlink, but that needs a click. Any
> > suggestions?