[web2py] IS_NOT_IN_DATABASE with a formatted value

[Ed Greenberg]

I have a table of US phone numbers in ten digit form. When I store
them, I take out all non-numeric characters using:

def cleanUpNumber(number):
    return re.sub(r'\D',"",number)[-10:]

I use a FORM() to get the numbers. Not a SQLFORM or CRUD.

I would like to use IS_NOT_IN_DATABASE(...) to make sure that I don't
get duplicates.

How can I get the validator to run the values through cleanUpNumber()
before looking in the database?

Ed