Hi Dawg,
The expression is simple, but can be VERY slow depending on your library size. You can try it on a calculated field, but I think it's best to use ZStats to run this expression once per day to update the Total Count daily (overnight), instead of trying to use it in realtime.
This expression should work for a calculated field:
listmath(fieldquery(name;artist,[name];[artist],number plays, 0, 1),2)
With ZStats you would run this instead (on the zstats.ini file):
setfield(Total Plays, listmath(fieldquery(director,[director],number plays, 0, 1),2))