If the programs use Installer from their own disk, just change the default tool to point to the version on your hard drive. Or run your version of Installer from the command line, specifying the program's install script as an argument.
If you're talking about a completely proprietary install tool, try Piru's advice, or try installing to RAM: and then move the program where you really want it. If it adds any assigns to your user-startup, make sure to change them so they point to the correct place.
