Regular expression for a string containing one word but not another

I'm setting up some goals in Google Analytics and could use a little regex help.

Lets say I have 4 URLs

http://www.anydotcom.com/test/search.cfm?metric=blah&selector=size&value=1
http://www.anydotcom.com/test/search.cfm?metric=blah2&selector=style&value=1
http://www.anydotcom.com/test/search.cfm?metric=blah3&selector=size&value=1
http://www.anydotcom.com/test/details.cfm?metric=blah&selector=size&value=1

I want to create an expression that will identify any URL that contains the string selector=size but does NOT contain details.cfm

I know that to find a string that does NOT contain another string I can use this expression:

(^((?!details.cfm).)*$)

But, I'm not sure how to add in the selector=size portion.

Any help would be greatly appreciated!

This should do it:

^(?!.*details\.cfm).*selector=size.*$

^.*selector=size.*$ should be clear enough. The first bit, (?!.*details.cfm) is a negative look-ahead: before matching the string it checks the string does not contain "details.cfm" (with any number of characters before it).

^(?=.*selector=size)(?:(?!details\.cfm).)+$

If your regex engine supported posessive quantifiers (though I suspect Google Analytics does not), then I guess this will perform better for large input sets:

^[^?]*+(?<!details\.cfm).*?selector=size.*$

regex could be (perl syntax):

`/^[(^(?!.*details\.cfm).*selector=size.*)|(selector=size.*^(?!.*details\.cfm).*)]$/`