need port on switch to be different IP address

A VLAN would be the most obvious choice, you have a good switch that is more than capable of it, so go for it.

Configuring VLAN on HP Procurve Switches
http://www.hp.com/rnd/support/config_examples/93xx_6308.htm
http://www.hp.com/rnd/support/config_examples/primary_vlan.pdf
http://www.hp.com/rnd/device_help/help/hpwnd/webhelp/HPJ4121A/configuration_vlan.htm

Technically, you don't have to create a VLAN for this, but it would be recommended to split up the broadcast domains and increase security.  If you don't use a VLAN, you just have to make sure your default router has the correct static route in place to route between the subnets.

I am not too good with v-lans but I did give it a try.  In building B I added vlan 99 and tagged port c1 thinking that this would give c1 a 192.168.50.xx ip address but it did not.  What am I missing?



192.168.50.1  (Bilding A)
------------------------------------------------------------------------------------------------------------------------------------------
vlan 1
   name "DEFAULT .50"
   untagged A1-A4,B1-B24,C1-C24,D1-D10,D12-D21,D23-D24,E1-E21,E23-E24,F1-F3,F5-F
   ip helper-address 192.168.50.13
   ip address 192.168.50.1 255.255.255.0
   no untagged D11,D22,E22,F4,F9,F20,F22-F24,Trk1-Trk3
   ip igmp
   exit
vlan 3
vlan 5
   name "v5"
   untagged Trk2
   qos priority 0
   ip helper-address 192.168.50.13
   ip address 192.168.60.1 255.255.255.0
   exit


19.168.60.1 (Building B)
---------------------------------------------------------------------------------------------------------------------------------------
vlan 1
   name "DEFAULT_VLAN"
   untagged A2-A4,B1-B4,C2-C24,D1-D24,E1-E24,F1-F24,H1-H16,Trk1
   ip address 192.168.60.4 255.255.255.0
   ip helper-address 192.168.50.13
   no untagged C1
   exit
vlan 99
   name "VLAN99"
   ip address 192.168.50.5 255.255.255.0
   ip helper-address 192.168.50.13
   tagged C1
   exit