I'm presuming that such a trigger would have better performance than the function (function has to work on every row where the computed column is selected, trigger catches the problem at the beginning)
I'll look into this, and work with the Dev on implementing one. Something to check for and replace anything non-numeric (depending on the requirements, maybe just strip it out)
I suspect we can start with the function as a foundation, just improve it some.
Once more, thanks Gail!