How to share the same USB device on more than on VM

[SoniaM]

Hello,
we have 3 VM with guest OS Windows 2008 on a real machine with Windows Server SP2.
We need to share the same USB device on 3 VM (or on 2 of them, at least), but seems it isn't possible.
When I launch the first VM, the USB key is mounted, but it can't be seen by the second one.
If I unmount the key on the first one and afterwards I launch the second VM, the second VM can mount the key.
However, If I unmount the key on the second VM to mount it again on the first one, I get this message on the first one:
Failed to attach the USB device "X" to the virtual machine "Y". Failed to create a proxy device for the USB device (Error: VERR_GENERIC_FAILURE).
I searched the forum and the tickets for that error, but I haven't found any solution for our configuration (more than one VM).

[mpack]

USB ports are not designed to be controlled by more than one PC at a time.

Typically, in a situation like this, one PC has control of the device and provides a server interface for other PCs. That is beyond VirtualBox's scope: the necessary drivers would have to come from the USB device manufacturer if they are not native to the OS.