[web2py] Grid: Pull field, but not display it, so it can be used by links

[naveed]

I like the grid a lot, but I think I am missing something. I have 2 fields 
called age and age_units. The age_units field is stored as an integer. I 
want to be able to show the age as a combination of the two fields 
including some processing to convert the int to the proper string unit. I 
am able to do this successfully using the links parameter. My problem is 
that, I can't hide the original age and age_unit fields. Is there a way to 
be able to pull a field, but not display it?