How do I bypass the security warning in the RDP Client everytime you launch it from a RDP shortcut?

The message title reads:

"The publisher of this remote connection cannot be identified. Do you want to connect anyway?"

There's a checkbox that reads:

"Don't ask me again for connections to this computer"

If we check that, it rights the following registry key:

[HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\LocalDevices]
"MachineIP or Name"=dword:00000004

I'm trying to bypass this warning by writing this registry values before I run the RDP. The problem is that the dword value varies. I found that in one machine (Win7), it was 4, but in another machine (XP), the value was 72 decimal. Does it vary depending on your OS, or is it by the RDP client version?

Other info:

1. Signing all my RDP files is NOT an option.
2. Checking the checkbox is NOT an option as we are trying to automate some stuff with a C# tool.

Thank you