htaccess regular expressions help

[vasiapup]

I need RewriteCond directive regular expression which sets a rule for RewriteRule to overwrite only those urls which _don't_ start, for example, with "posts/new/"
Do you know how to do it?
I know how to do it for urls which start from an expression.
But for those which DON'T start... I tried many times, but didn't succeed.
Help, please.

Also how to detect urls which DON'T contain, for example, "/(two_numbers)/"
?

Thank you in advance

[jdMorgan]

Use the NOT operator, which is "!"

RewriteCond %{REQUEST_URI} !^/[0-9]{2}/

Jim

[vasiapup]

Thanks a lot, Jim!
Your help is really valuable!