is a construct for use inside AskFunction that gives the value associated with key, or Missing[…] if none has been provided.
If a value has already been associated with a key, AskedValue returns that value just like Ask. But unlike Ask, AskedValue will never request a value from the user, instead returning Missing[…] if no value has yet been provided.
When no value is yet known for the requested key, AskedValue["key"] returns Missing["NotAsked","key"].
AskedValue returns the value whenever it is already known:
But returns a Missing object whenever it is not known yet:
AskedValue returns the value without causing a form to be displayed: