Just assign the interface in question another IP address, so
switch(int)# ip address x.x.x.x/xx
Even though you already might have a IP address assigned, this will add a secondary address to the interface. I know on Cisco's you would have the ip address statement along with the secondary (ip address x.x.x.x x.x.x.x secondary), but HP doesn't need the 'secondary' command along with the 'ip address' command.
Hope that helps.
P.S. to get rid of a address later, just add the 'no' in front of the 'ip address x.x.x.x/xx'