Syncing Apps from HOME and WORK?

Let's say I have 10 downloaded Apps on my iPod touch from the App Store and I have them all synced at home. Then when I get to work, I notice that there's a new cool App that I want and I want it on my iPod touch, iTunes says it's going to erase all of my Apps and replace them with the ones from my work computer (including the data files) meaning all of my settings and personal changes to my apps (such as AIM ID and Favorite Radio Stations) will get reset. How do I avoid this from happening? I tried just dragging the App to my iPod and it won't work. Anyone have a hint on what I could do?