You may try IBUtils at www.riverdata.cz/ibutils/ibutils.htm. This tool
enables to create new tables, fields, indices, referential integrity -
all in simple "CASE LIKE" GRAPHICAL INTERFACE. It supports SCRIPT
TEMPLATES.

ALL METADATA CHANGES ARA LOGGED INTO SCRIPT, so you can reproduce the
changes to another database(s).

And it is free :)

HTH, Ales