Removing one keyword

Dear all, 
accidently I assigned a keyword ("phase II") to all the references in my
library (> 2000 records) using the "Change and Move Fields" function.
Does anybody know how I can remove this keyword from all records without
deleting the other keywords (I could export all references and then use
the replace function in a text editor / MS Word and re-import all
references. However, I would need to set-up a complex output style)? 
Thanks for any help in advance 
Sven