Raise error when attribute is empty.

How do I raise an error when an expected attribute is empty?



I'm trying this:

                Set objUser = GetObject("EDMS://" + strDN)
               
                ObjUser.GetInfo
                               
                FTPRoot = ObjUser.Get("msIIS-FTPRoot")
                FTPDir = ObjUser.Get("msIIS-FTPDir")

But if the attributes are empty I get an error.  It's nice I get the error but I wanted to possibly have the user properties for the empty attribute pop up so it can be populated.  Or in the very least replace the current error with something more friendly.