In 2003, how do I create a slide with the following characteristics:

------------------------------------------
Title

Line One
Line Two
------------------------------------------

1) When the slide opens, Title is black, and Line One and Line Two are gray.

2) Pressing the space bar causes Line One to become black. Line Two
remains gray.

3) Pressing the space bar again causes Line One to become gray and Line
Two to become black.

The objective, of course, is to shift the reader's focus to the line
being discussed. It can be done by creating three slides and switching
between them sequentially, but I'm sure that there is an easier way,
probably with animation.

Thanks!