Syncing a New Catalog between PCs

I typically open a new catalog for each individual project that I'm working on to keep everything separated.  For the last 8 months or so, I have been doing all of my editing (LrC) solely on my laptop due to travel.  Now that I am home, I want to be able to sync with my desktop PC, which has also been using different catalogs than the original LrC sync catalog. 

How do I change my LrC sync catalog to be the same on both PCs so that I don't keep getting the "you are currently syncing "xxxx.lrcat". Would you like to switch to this one instead?" message?

Is it even possible?