I want run a virtual machine (Windows 7 system, named "Win7Office") on a remote PC (10.32.1.81).

Modify VM config

Start VirtualBox GUI (locally via physical monitor and keyboard connected with host 81, or via VNC). Check "Auto-resize Guest Display" in vm's Settings -> View menu. Then start Win7Office, verify if vm run properly. Once OK, close this vm.

Use VM remotely

On client, run following commands:

ssh 81
xpra start :111 --start-child="VBoxManage startvm Win7Office"
exit
xpra attach ssh:81:111

Once done, use xpra detach ssh:81:111 to detach from this VM.