Lowest and highest User ID numbers

I would like to write a script that updates a particular custom field before a user list is generated. I already have the code to update the field when the users profile is viewed, but now I want to be able to add a cb userlist menu item that will, when selected, show the user a list with the fields updated. This removes the step of having to view the profile first to get the field updated. I'm assuming I need to register for an event trigger, which I did. My next step is to have the function that updates the fields. I need to have a For loop to index through all of the users. I was going to use the user id field to do this, like so: Problem is, I don't know how to get the two variables, lowest and highest user id.

any help?

do a query sorted by userid ascending and take the first.
do a query sorted by userid descending and take the first.

you have your min and your max.

Thanks for the reply. I guess I'll look around and see how to do that from inside php. Seems like there should be an easier way.

Ok, So I got the userid range, but now I can't see how to update the field for each user. How do you use the userid to update a field of that userid? I saw your tut on establishing the cbUser object but that always returns the logged in user. I need to be able to do a for loop that updates a field based on the userid. for example:

Any help on this?

change $myId = $_CB... to $myId = $i