LD WATCH LDan: lbn [,lbn...]

 	This command will set a watchpoint on a virtual or logical
 	blocknumber on the specified device. The lbn is ignored on
 	I/O functions which don't need an lbn (IO$_PACKACK for
 	example).

 	This makes it possible to let the driver take some actions
 	dependant of which lbn was accessed with a specified function-
 	code.