Yes, you can do this.
When you are ready to move from one computer to the other, all you have to do is export the lot from the neighborhood view by clicking on the lot and choosing the "Share" button. The game will then package up the lot and put it into the Documents\Electronic Arts\The Sims 3\Exports folder, under the same name of whatever you called it when you shared it. Simply take that file to the other computer and install it, and the lot will then be in that game as well, exactly where you left off building it at! Once the lot is on both computers, though, changing the lot on one of them will not update it on the other. You will have to re-share it to a new file every time you want to move it between computers.