Google alerts: How to not include results from certain sites or keywords?

So I've been using google alerts and I was wondering if there was a way to use the -subtraction method? Doesn't seem like there is a way to do that.

For example, if you want to hear results for "SEO" but but not from Moz.com how would you do that? In the search field you would type in:

seo -moz

And no offense to Moz.com just the first thing I thought of.

Actually I am searching for a step van, but get results from sites I don't want or don't want a food truck.