Properties editor/expression builder

[Gotheallblacks]

Are there any custom written Properties editor and expression builders out there. My purpose is for using on memo feilds for variable inventory types/info ie a base inventory record(s)in a inventory parent table with the memo holding xtra addable properties and formulas(for adding such as weight,colour,cubic and virtually anthing) with the child inventory table having a memo field inheriting properties from parent but overiding with its own properties. Much the same as class and form table files.
Thanks in advance