I have a general purpose updating routine which deals with a number
of tables. The trouble is that it must not update columns which are
foreign-keys for another table. So I want to know given table xxx
what are the names of the columns which act as foreign keys.

I have dug into the RDB$ stuff and can vaguely see a roundabout way,
but I thought the SchemaCache could lead me directly to it.
This has a 'Foreign Keys' entry. Which lists what I want as
keyname,tablename ie a comma separated pair.
I want a list of foreign keys existing in a given table.
I have tried to understand tib_stringlist and looked at the source
but the boggle-factor sets in.
Any Pointers or help would be appreciated.
Regards Dave