Sam,

> I need to create some upgrade scripts which have a "if not exists" in
> them, since some customers have the element others don't. Does isql
> support this type of thing? If not, any suggestions on how to
> implement it?

a combination of EXECUTE BLOCK, EXECUTE STATEMENT and querying the
system tables might allow you to get what you are after.
CREATE OR ALTER might also be of some use.
--
Nando Dessena