Receptional_Andy - 8:44 pm on Jun 24, 2010 (gmt 0)

Google will certainly block you if you make multiple requests in a very short period. As you've experienced, more advanced search syntaxes are likely to trigger this process more quickly.

I've found if you leave a reasonable gap between queries it's pretty rare to trigger the blocking.

I'm not aware of anything software wise that I could recommend to do this with, although a little PHP is more than enough.