toc of only half of an article

[Robert Neumann]

Hello,
I have an Article with 40 Sections. Now I would like to have a toc which 
contains only the first half of the article. 
(Actually I reset the sections counter after 20 Sections and start because the 
second half of the sections are a kind of repetition of the first ones)
Is there any way of doing this??
Thanks
Robert