Virutalbox Portforwading [NAT] help

[jakes9x]

I want to forward both tcp and upd ports on virtualbox
I successfully forwarded tcp port using this command
C:\Program Files\Oracle\VirtualBox>VBoxManage.exe modifyvm "vbox" --natpf1 "guestssh,tcp,,81,,81"
And i got sucess. I checked it at http://canyouseeme.org

But i also want to forward udp ports
I tried to forward udp ports using this command
C:\Program Files\Oracle\VirtualBox>VBoxManage.exe modifyvm "vbox" --natpf1 "guestssh,udp,,81,,81"
But it showed me an error " A NAT rule of this name already exists"

What do i do ?

[Technologov]

change rule name to "guestsshudp" or something...

in v4.0 there is a GUI making it straightforward