You can do that with PowerPoint 2002/XP and above.
First, create a textbox and have the ticker text you want.
Move the textbox out of the slide at the bottom right hand corner.
Now, click Slide Show > Custom Animation.
Click Add effect > Entrance > Crawl In / Fly In.
Adjust the speed to your preference.
Next, right click on the effect, select Timing.
Click on the Repeat dropdown field and select "Until End of Slide".
Is that what you want?
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PowerPoint Heaven - The Power to Animate