[Zope] Help with editing Product dtml files

[Piers Lauder]

I'm making a Zope "Product" for managing and creating student surveys
(which I hope to contribute via zope.org) but I'm having trouble with a
couple of techniques:

1.	How does one enable a dtml file that is instantiated as in
		my_dtml = HTMLFile('my', globals())
	available for editing in the products' management screen?

	There's probably more to this - as at the moment the management
	screen goes straight to the "index_html" form as with the "Poll"
	Product.

2.	What's the approved way to catch database errors in methods?

	I'm creating tables on the fly, and need to check if the table
	exists before trying to create it. (I'd use a "tables" method if
	all the database interfaces supported it. I'd also use a try/except
	but the database objects have different names for their exceptions.)