[R] unlock package environment ?

[Ferdinand Alimadhi]

Hello,

Somewhere in my S3 package "foo" I want to create, on the fly, a  new S4 
class which extends another S4 class "bar".

setClass("fooS4bar", representation("bar", bar.data = "data.frame"), 
where = parent.env(environment()))

where "where" is the environment of my "foo" package.


But I get:

Error in assign(classMetaName(Class), def, where) :
        cannot add bindings to a locked environment

Is there any way to unlock the package environment, add a binding and 
lock it back?  How the environment of my own package got locked on the 
first place?

Thanks for your help,

Ferdinand