You can create another port group on the same virtual switch on a specific vlan (i.e. 10) and the NAC traffic on that port group that will leave the same physical port on vlan 10. everything on VMNET10 will also see that traffic tagged as vlan 10.
Hi Antonio,
I believe you'll be better off configuring this on the vSwitch (assuming VMware) so that you can ensure the traffic leaves the host tagged.