You can't modify the slide transition apart from using the default ones
given. One way you can do is to make use of custom animation to achieve the
crossfading instead. To do so, you can do a print screen on the second slide.
Then, paste the screenshot. Add Entrance > Fade effect onto the screenshot
and modify the timing.
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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