screenrc

I've been using screen more and more out of habit recently. I used to use a lot of tabs in Gnome Terminal on each project I'm working on. Now I run one terminal per project with a screen session for all the sub-sections. It seemed a good time to revisit my .screenrc which looks something like:

# Ensure we run a fresh login shell  shell -${SHELL}    # I want more scrollback  defscrollback 2048    # Set the caption to show:  #   current window  #   other windows  #   date/time    caption always "%{+b Rk}@%H%{kk} %{Yk} %n %t %{-b -s}%{kk} %{wb}%W %=%{kk} %{wB} %c %D %d %M "

The only missing bit is getting the session name in there somehow. I've tried various experiments with the backtick command and echoing $STY but I expect it's not available to the context the script runs in.