Accessing field of OLD in trigger

Hi,

I'm working on a row level plpgsql trigger running after delete, using 
a 8.0.3 server. It gets a parameter which is a field name of the OLD 
record. How can that field be accessed?

I'd like to do something like:

for recvar in 'select OLD.'||quote_ident(TG_ARGV[0])...

Daniel