Spell checking of a paragraph

Hello,

I am currently searching for info on how to make a spell check from  
vim of a paragraph only.

Imagine to have a large file, which you already spell-checked. Then  
you make some changes at the end, and you want to spellcheck it  
again. If it is a latex file, with formulas, etc... and you will find  
plenty of spell errors (which actually are not errors) before you  
reach the part you really want to check.

Anybody knows how to do this (apart from saving the paragraph in  
another file...)? A simple enough option would be to tell aspell  
WHERE to start, which line of the file. Is it possible?

Thanks,
Sandro