||There isn't a hot key for this and, to the best of my knowledge, there isn't a command tag sequence that will do this either (if there were then you could assign the command tag to one of the custom buttons on the toolbar and execute it that way).
That leaves only one way to do this (short of Slaven adding either hotkeys or commnd tags), that being to use one of the junk mail scripts that John Dearinger has written. These scripts perform the indicated function and move the message to the trash:
Once you have downloaded these scripts you can assign them to the custom buttons on the Poco toolbar and then invoke them by clicking that button or using the short cut key assigned to the button.
Unfortunately no one has created an equivalent script for banning the subject.