That would probably be a dangerous way of doing things, especially if you were running two different versions of NetLogger. I wouldn't recommend it.
I'd suggest making your "home" NetLogger setup contain the primary log for NetLogger. Before going portable, export all your contacts to a file in ADIF format. Then on your laptop, clear out all of your contacts from a previous session by selecting them all and then clicking the delete contacts button. Finally, copy the exported adif file from your main system to your portable system and import them all. NOTE, if you forget to delete the contacts on the portable system you will likely wind up with lots of duplicate contacts on the portable system.
This way you'll have all your contacts so you can tell which ones you already made contact with, etc. While portable log contacts on your portable system. Then when you return, select ONLY the new contacts (you should be able to figure out which are new by the contact date, or by checking the last contact you made on your home system), and export the new selected contacts to an adif file. Make sure you don't export everything, i.e. the ADIF file should only contain the new contacts you logged. Then copy that file to your home system and import the ADIF file. That will add the new contacts to your home system.