[pietvo]

When you open your book in OpenOffice.org, and click on the chapter titles you will see that they are all Heading1 or Heading2. Probably Microsoft Word will show the same. Now open the file in Calibre and click Convert E-books. Click Structure Detection and in Detect chapters at, enter the following expression:

//*[name()='h1' or name()='h2']

Now convert to EPUB.
Find the generated ePub file in the Calibre document directory and open it in Sigil (or some other program that can open the CSS file for you). At the end of the CSS file enter the following code:

h1, h2 { text-align: center;
	text-transform: uppercase;
	font-weight: bold;
	}