Hi Aaron,
I'm not sure about DFM 4.0.2, but in DFM 5.1 you can specify the number of seconds in the past using:
-d Duration for which data is to be retrieved (in seconds). The time is
calculated going backwards from the current time. When this option
is specified, start-time and or end-time are ignored.
So setting -d 604800 should give you the last 7 days from the moment of command invocation
Kind Regards
Chris