Named_scope lambda syntax

How would I pass an attribute name into a named_scope lambda?

I want to be able to search an active record class for nil values in a
particular attribute. Would like to use a named_scope instead of find
() because I want to tack other methods on the end of the result.
Syntax I’ve tried:

workouts table in mySQL:

attributes time, reps, weight, distance

class Workout < ActiveRecord::Base
named_scope :no_score, lambda {|compare| {:conditions => ["? IS NULL",
compare]}} # tried all these
named_scope :no_score, lambda {|compare| {:conditions => {compare =>
nil }}} # forms of syntax
named_scope :no_score, lambda {|compare| {:conditions =>
{compare.intern => nil }}} # with no success


Any ideas where I"m going wrong with the syntax?

never mind, I sorted it out. Solution:

named_scope :no_score, lambda { |compare| { :conditions => “#{compare}