Changing the textwidth

Question

Is it possible to change your text's width couple of times in one page? I would like to start the document with couple of lines that have been placed closer to the paper's edge and then return back to original textwidth after the headline. I have tried placing

\addtolength{\hoffset}{-0.75cm}

at the start of the document and after it "corrected" the width with

\addtolength{\hoffset}{0.75cm}

but the document counts these two together and every line starts at the document's original textwidth. This is what I have tried:

\begin{document}
\addtolength{\hoffset}{-0.75cm}
This should be\\
closer to the edge\\
but it isn't\\
\addtolength{\hoffset}{0.75cm}
\begin{center}
Topic
\end{center}
And this should be at the document's original textwidth where it really is.
\end{document}

I tried to use \setlength but this time it only reacted to last command, which returns the width to original. Using \newenvironment might be the solution but I couldn't get it to work. I used

\newenvironment{headline}{\setlength{\hoffset}{-1cm}}{\setlength{\hoffset}{-1cm}}

with no success. Don't know if I did something wrong there or why it doesn't work.

I would be happy if someone could solve this problem or tell me that going back and forward with widths isn't possible in one page.