All you need is an 2nd window screen for the window
that faces the daytime and evening sun, which would
be the window bees buzz against in attempts to leave.

You want some metal wire screen, not the plastic stuff.
(The screen in the window could be plastic or wire,
but I like using metal wire for the window too.)

Take a small piece of wire screen, and cut it into a
square roughly 5 inches on a side.

You are going to make a cone-shaped bee escape
from the wire screen, so if you have one of the plastic
ones, use it as a standard for comparison.  If not, here
is what they look like:

http://www.dadant.com/catalog/images/items/M00911l.jpg

Drill a 1-inch or larger hole into a 2x4 scrap to make a
work surface.

Take a bluntly pointed object about the size of a fountain
pen, and, holding the screen flat on the wood, press
the tool into the screen.  You are making the "pointy"
part of the cone.  Press slowly, and you will see the
cone form.

When you are done, you have a cone with a flat area of
screen around the base.  Take a pencil, and insert it into
the tip of the cone to make the exit hole just large enough
for a worker bee to squeeze out.

After you have made and discarded about 6 of them,
you will be able to make a few that are decent.

Cut holes in the screen mounted in the frame, and pulling
a few of the "horizontal" wires at the flat edges of the
screen cones, leaving individual wires that radiate out
from the base of the cone about an inch.   Weave them
into the window screen around the holes to create a secure
mechanical mount for the cones.

Oh yeah, the cones must point OUT, not in.  :)

When it is extracting time, remove the normal screen and
insert the "escape-equipped" screen.   Bees will leave,
and bees attracted by the smell of a metric ton of honey
will not get in.

You will have to fiddle with them, and the plastic ones would
work just as well if you drilled small holes in the bases, and
wired them to the window screen, but the wire-mesh versions
are invisible, do not block your view, and don't look tacky.

A complicated description, but I have seen old guys make
perfect ones in seconds, so maybe your best solution is
to find a beekeeper with significant gray hair.


                jim