[web2py] Getting table a to use as default string from field in table b

[tsvim]

Hi all,

I have 1 table with a lot of fields. Some of them, I want to have a default 
value dependent on the user.
In the user table I have a field called default_x. I tried setting the 
default for field x in the data table to 'user_table.default_x'. Which did 
not work.
Any ideas how to achieve this functionality?