Air Conditioning isn't cold when still 97 Sidekick

I have had a 1997 Suzuki Sidekick for 5 years. The air has always been not real cold when sitting in traffic. Its gotten worse this year. I have spent about $400 over the past 2 summers trying to find out whats wrong. No one seems to know. No leaks. Condenser fan replaced. Nothing seems to help. Good and cold when moving 45 mph or more.