Can gcal automate highlighting days on|off for this "shift work" roster?

I've been reading the man page for gcal, and I'm unsure if I can do the following: Description: I would like to print a roster with the output like cal -y but highlight all days a person is rostered on. The Roster is a repeatable pattern of: 4 days on, 3 days off, then 5 days on, 4 days off. (This pattern repeats over the whole year) start from date: [year,month,day] for the whole year: { highlight 4 days // Working skip 3 days // Days off highlight 5 days // Working skip 4 days // Days off } print output to screen as year calendar thanks for your time.