freezing a particular field in a table

[Ferindo Middleton Jr <fmiddleton@xxxxxxxxxxx>]

Is there a way where you can implement a situation in a postgres table 
where a particular field cannot be changed when saved initially. I have 
table and there's one particular integer field that should never be 
changed in any record inserted... but I might need to allow the entire 
record to be deleted... I was just wondering if there's a way to 
implement something like this on a field (but not the entire row) at the 
database level?

Ferindo Middleton