Functions refering directly to table columns?

[cluster <skrald(at)amossen(dot)dk>]

When using a function I need to parse each value as argument, e.g.
  myFunction(arg1, arg2, ..., arg999)

However, if I can guarantee that the function will only be used with a 
certain table, can I then omit the arguments and letting the function 
refer to the table columns directly?
In that way I could just write
  myFunction()
which is much easier. Furthermore, if I redefine which columns the 
function should use, I would only have to modify ONE place, namely the 
function definition. Not tons of queries.

How can I obtain this non-argument-requiring function feature?