nlapiSubmitRecord ... "Record has been changed"

I'm writing a script that will create a case record when someone saves a customer record. Here's my problem. When I try to do this in a client user event script in a "Before Submit Function," I get an error that reads, "Record has been changed."

The NS documentation says that I might get an error when I do this, so I understand that's where I'm going wrong. However, if I create the case as an "After Submit Function," I no longer have access to some global variables that I need. In particular, I'm storing the initial values from some fields in global variables so I can test to see if the user changed the values of some fields. I compare the global variable with the new value of the fields. But I don't think I can do this comparison if I fire off an "After