Melt some candle wax around the wound to seal it, then wrap part of a latex glove around that, then secure all with a splint ie a tongue depresser or something such as that, taped all together, to stabilize the break. It should heal itself in about a year.

Kay; thanks for the tips which I'll save for next time. I just saw your post, and of course by this time the branch is long dead. I should have checked back sooner! Anyway, I'll probably have plenty others to work on since they will be cladding the entire house in vinyl in a few weeks.
My main problem was I was thinking it should be open to the air, and by your method it would be sealed. I know my idea didn't work, so I'll try yours.

You might want to stock up on some grafting tape too. It is kind of stretchy, very easy to work with, and does a wonderful job of holding everything together.

Janie

Thank you, too. I will get some grafting tape.

Through the years I have repaired broken branches of apple, pear, cherry, amelanchier and viburnum (probably others) with common masking tape. Always taped them up immediately after accident/discovery. Removed the tape after a couple of months, and you couldn't tell they'd been damaged. If damage is low on branch and the weight is heavy, trim the branch at a slight angle just above a leaf node to lighten up the load.