unix diff with numerical precision

Hi,
I search a unix utility to diff two files, that takes as argument numerical precision as well. If two files are different only in numbers and the difference is less than precision then the result as they are the same.
The precision may be absolute (x1-x2) or relative (x2/x1). Also I need the possibility to have a gui front end, like tkdiff.
Thanks

It is very unlikely that any such utility exists in unix or any other O/S.

A custom program will require an expert.