Perhaps you are trying to fix the wrong thing.

If the call logger is creating huge temporary files, it must be doing it for a reason.

Either it needs them (in which case you shouldn't be deleting them) or it doesn't need them in which case you should get onto the software supplier for a fix.

Also consider that if the files are being created all the time, then cleaning them up during login is not going to help much. You will either need to schedule the job to run regularly, or give the users a "purge" icon on their desktop to run the job and clean up.

However, I'd go for getting a software fix. It's unreasonable to expect your users who should be busy at their jobs to be taking time out to clear up after a dodgy application.