Help with Joomla's Template Creator extension in centreing divs

I am using a Joomla extension called Template Creator CK to create a template and I have added 2 wrappers and set them to full page width. However I want the module blocks in the wrappers to be centred and have a width of just 1000px. I need to know what I have to enter in the custom CSS boxes to achieve this effect. NOTE: I do not want to do this by directly editing either the [login to view URL] or [login to view URL] files. This is because every time I make changes to the template layout and design within Template Creator, new CSS files are generated by Template Creator. The freelancer must have knowledge of Template Creator ([login to view URL]). I don't want someone coming along then wasting both their time and mine without a clue how to do this.