dsquery / dsmod active directory users

here's an easy 500 points for someone

i have about 200 users i need to modify the active directory attribute called "web page" from one thing to another.

many of these users need to have a completely unrelated site in there, and not changed, and are not part of specific OU's or groups

can i use any AD command-line things, that can say something like:
"look at all users, if their 'web page' is http://www.foo.com, change it to http://www.bar.com"  ?

for clarification:
200 users in "users" OU
180 of them need to change from foo to bar (as above)
20 of them need to stay exactly as they are and not change at all