How to specify a variant in 'depends_lib'

I am trying to write a portfile for some software but I want to make sure that a particular variant of a dependency is installed. Is there some way that I can specify the variant within the portfile that I want to use? WOuld something like: depends_lib port:otherport+variantname work? (I'm away from the computer that is doing this at the moment so I can't experiment). If not, then I'll have to think of some other way of achieving my goal. Thanks Susan