What exact graphic pad or tablet do you mean and what exact virtulisation software (Parallels Desktop or VMWare Fusion) do you use with what host and guest OS?
Normally, graphic tablets do not need to be ejected to be usable in a VM, but simply disconnecting it physically and connecting it physically again might do the trick, as the virtulisation software will ask, where to connect that device to.
It's a trust flex paper thin graphics pad, mac os x host, windows 7 guest. It shows up under the devices menu in virtualbox but is greyed out. It works great on mac