I wonder how. I've updated a mod, but the problem is it is supposed to be affected by another mod that is an esp. But I can't get it to be dependent on it. I've tried ESMIfying it via Bash and making changes and saving it, but that didn't help. I know it can be done because I use mods that are esp's dependent on esp's.

have a look at this page:
http://cs.elderscrolls.com/constwiki/index.php/De-Isolation_Tutorial

It may have something on it that is useful for you.

Good tutorial link. Thanks. I'll see if it works.

It's much easier to use TES4Edit to do esp mastering.

Open TES4Edit. Make sure the original mod and the new mod are checked and are sorted by load order.
Click on the + next to the new mod.
Right click every record you did not edit and select Remove. (Except File Header)
Click Yes
Right click on the new esp again and select "Add Master"
Check the original mod.
Click OK
Right click again on the new mod and select "Sort Masters".
Right click on each remaining record and select "Change FormID"
Change the first 2 digits to match the first 2 digits of the original esp.
Click OK.
Close TES4Edit, check the mods to save.

Thanks, aellis. It turns out that ESMifying the esp via Bash does work. I just wasn't loading the ESMify'd plugin. Doiee! :blush2: