question about presentations

["Mr. Wang Lei" <lwang@Amath8.amt.ac.cn>]

Hi, I have some questions about presentations created by
context. One is that I want highligt an itemize on the
beginning and then the next, for example, I have 3 items

item 1
item 2
item 3

at the beginning, the item 1 is marked by red and others
marked gray. when I click mouse, item 2 now marked red and
item 1 and item 3 now is gray. and so on. how to implement 
it? 

Another question is that Can I hide a text block and then
display another textblock in the same place? for example,
there are two paragraph in one page, 

Paragraph 1 
Paragraph 2

When I click mouse, the Paragrap 1 hides and a new Paragraph
3 is displayed in where the Paragraph 1 was placed before.
I am sure the Paragraph 3 is samller than the Paragraph 1,
so it may not result in the pagebreak problem.

Greets,

Wang

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Mr. Wang Lei                      Phone: 86-10-62616670 
                                  Email: lwang@amath8.amt.ac.cn
Institute of Applied Mathematics         leiwang@btamail.net.cn
Chinese Academy of Science        Address: P.O.Box 2734, Beijing, 100080  
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