Submit form on enter without focus

I have a search form on my site. I would like other people's thoughts on this idea.

The flow goes like this: The user will type in the search field with the checkbox selected by default, and then click Enter to submit the form. However, if someone does not want the checkbox ticked, they will lose focus on the form by unchecking it, causing them to either:

• Click the magnifying glass or
• Refocus on the form and click Enter.

Would it be better to have Enter submit the form regardless of focus?