From the knowledgebase:
It is possible to do a silent installation of the Mobile VPN with SSL client software on a Windows computer. When you install the Mobile VPN with SSL client on a computer, the network adapter (TAP driver) requires administrator privileges on the local system to install correctly. You can run a script on the computer as administrator, and then use these command-line options to hide any message boxes or prompts from the user:
[executable filename] /silent /verysilent
If you need to use a specific install location for the application, you can use this option as well:
/dir="c:\directory\path"