@Jennifer Jinhong has posted about how to use a "dynamic promptset" behavior that you might find useful.
https://community.automic.com/discussion/1020/dynamic-promptsetAnother option would be to re-word the question to "If we have data, should we deleted it".
Another option would be to use script and the :READ function to prompt the user at the right time.
Another option would be to install a CALL/Notify step that asks for user input at run time only if there is data.