Getting # of days until expiration

[Brian Dunning]

I have a DATE field that includes a date sometime within the past 30  
days. I'm trying to show the number of days until the expiration  
date, which is 30 days in the future from the date in the field. I've  
tried a bunch of permutations of something like this:

select (30 - SUBDATE(CURDATE() - datefield)) as expiration_days

All my permutations give me errors. Can someone set me straight? I'm  
hoping to get an integer between 1 and 30 (30 day old records are  
purged separately).

Thanks....