charnny,
there is one method, however it is unreliable and depends solely on caller's wish to listen to announcements and press some digits or anything. there's a field "return destination" on the vdn form page 2. you can fill in a "return questionnaire" vdn here. when a call was processed and agent pressed "release" button, caller will be connected to this "return destination" vdn. the rest is simple: create a vdn with vector like this:
01 collect 1 digits after announcement y (press 1 if you were satisfied or hang up if not)
02 route-to vdn xxxx if digits = 1
03 disconnect after announcement z (thank you for calling, good bye)
after doing that, you'll see how many callers were connected to "return" vdn by running vdn report, and by running report on vdn "xxxx" you'll see how many of them were satisfied. i simplified it, but like that.
note that like any method that depend on caller's will, it's unreliable by default.