Microsoft Word 2007 – Force Word Count for Specific Part of Document

Use Maj + Enter. This will add a carriage return instead of a paragraph mark.

Based on this answer for previous versions of Microsoft Word, I've found the following manual solution to my question:

1. In the 'Home' ribbon-bar thingy, click on the small pop-out expandy-button in the far bottom right of the Styles group (which shows the Styles window - Alt+Ctrl+Shift+S)
2. For the desired Style you want a Word Count for, click the drop-down next to the style name, and click 'Select All x Instance(s)'
3. The Status bar (bottom left) gets updated with the Word Count for the selected Style (or you can open the 'Review' ribbon, and click 'Word Count' in the Proofing group - which also works on the current selection).

Bonus tip - you can hold the Ctrl key while clicking the 'Select All x Instance(s)' of another Style to have multiple Styles selected!