Generating Foreign Key Script

We sometimes get very large databases that we want to cut down to use for
testing.

The information is all related to a central accounts table.

The way I thought of doing this is to grab all the foreign constraints and
turn them into cascade delete constraints, then delete as many accounts as I
want.

After this I will restore the constraints back to their original state.

I am having a problem doing this as I cannot find a way to programatically
get the add constraint foreign key sql.

For example, I can use sysforeignkeys to list all the foreign keys or
ADO.OpenSchema(adSchemaForeignKeys...) but this doesn't give me the actual
SQL to modify.

My idea was to go through the database saying:

alter table (tablename) drop constraint (foreign key)
alter table (tablename) add constraint (foreign key) on delete cascade

delete various accounts and related data

alter table (tablename) drop constraint (foreign key)
alter table (tablename) add constraint (foreign key)

Can anyone assist?

Thanks