I'm baffled and intrigued as to what/why the op is trying to do and what effect is he trying to create using what drums?
I'm guessing you just want a normal open hat being closed by the closed hat?
As Jonesy pointed out BFD does this naturally and also has a very flexible choking system but surely all drum vst's will have the basic function where an open hat is closed when you hit the closed hat?
Why are you using to different instruments? I'm guessing perhaps these are electronic drums sounds and not acoustic ones since you say you can hold a note down to make the open hh longer?
I don't think you can do that in any acoustic type drum plug in.
Steve