How can I achieve an effect like the following using Microsoft Word 2010?

I want the gray background to extend up to the edge for every title but I can't achieve this.
How can I achieve an effect like the following using Microsoft Word 2010?

I want the gray background to extend up to the edge for every title but I can't achieve this.
Word is not able to do what you seek with standard text or paragraph formatting. You will need to insert a text box and format it the way you desire.

Text boxes use absolute positioning, so you can move it where you need without issue to the paragraph or page formatting.
I think this is a reasonable approximation, and I've highlighted what I used to achieve it (the margin and tab stop settings are only applicable to that title line):

