Remove older file (only) from NAS

hi there,
so here's what i've got so far. i'm a wordpress dev, i have backup's automatically sent to folders in my dropbox (db, plugin's & theme backup's). db is a scheduled backup & remains in dropbox.
plugin's & themes are on demand.
as soon as a file plugins-*.zip appears in a dropbox folder, it's moved to the corresponding folder on my nas.
this is basically to keep my dropbox storage under control & to allow me to run archive backup's on the nas.
this is running spot on.
the zip files that are created contain a random hash in the file name, so they are going to be different every time they are created & subsequently moved to my nas.
plugins-12345.zip, plugins-6789.zip - you get the idea.
what i'd like is a rule that will run on that nas folder, say weekly, monthly (or on demand), that will trash the older zip file (only).
is this even possible given the file names won't be the same?
also, (newbie question here) want happens if the dropbox - nas rule runs if I'm not on my local network, will it automatically re-run when it's next attached to the nas?
thanks for reading, any pointers very much appreciated,
Jason
so here's what i've got so far. i'm a wordpress dev, i have backup's automatically sent to folders in my dropbox (db, plugin's & theme backup's). db is a scheduled backup & remains in dropbox.
plugin's & themes are on demand.
as soon as a file plugins-*.zip appears in a dropbox folder, it's moved to the corresponding folder on my nas.
this is basically to keep my dropbox storage under control & to allow me to run archive backup's on the nas.
this is running spot on.
the zip files that are created contain a random hash in the file name, so they are going to be different every time they are created & subsequently moved to my nas.
plugins-12345.zip, plugins-6789.zip - you get the idea.
what i'd like is a rule that will run on that nas folder, say weekly, monthly (or on demand), that will trash the older zip file (only).
is this even possible given the file names won't be the same?
also, (newbie question here) want happens if the dropbox - nas rule runs if I'm not on my local network, will it automatically re-run when it's next attached to the nas?
thanks for reading, any pointers very much appreciated,
Jason