Module: Override mandatory Moodle content

Hi,

How do I override style of main mandatory content of the moodle page from within a module? The module in question is the quiztimer.

I am refering to the 

<div id="region-main">

Which containt the style

.side-pre-only #page-content #region-main {
margin-left: 200px;

I need to add "margin-right: 200px;" to allow space for a floating quiz timer on the right. But all my efforts are efficiently ignored.

How do I add this element style to the quiz module? Thanks!