|I'm afraid not. Office has to "discover" all available drives so it can build a save or save-as window with all of them in the list. When it comes across a drive that Windows says exists but it can't access (an unavailable network drive, for example), it waits for a period of time and if there's still no response, it moves on. This can cause quite a delay, especially if there are several in-accessable drives.|
The easiest thing to do is to disconnect network drives when you're not connected to the same network and re-connect when your are.
If you access network resources from the "My Network Places" folder, then you can simply open them again from that folder to re-activate the connection. If your network folders are mapped to a drive letter, then logging off and back on to the domain should re-map the drives.
If your system is only slow when at home and connected to your workplace, you might experience performance problems because of the remote connection. If you have multiple mapped drives and you don't need access to all of them at the same time, you might consider disconnecting from those you aren't using.