This is something that requires a degree of processing by the script itself. In the case of Blocs, the in-built form processor, although adequate for most needs, doesn’t have the more sophisticated abilities of a full-blown form processing script.
I’ve overcome these limitations by making HTML forms externally and then including them into Blocs via the HTML widget. This allows me to post the form to a script on my server that has the ability to process data in other ways. For example, selecting a department or individual from a drop-down list will send the form to a specific email address. The reason an external form is able to do this is that it can be made with the hidden or derived fields that are required to perform this type of processing. It maybe that hidden fields capability and submission to third-party scripts will become a feature of Blocs in the future, but for the time being, an externally created HTML form and a good self-hosted script, such as Tectite Formmail, will do this type of processing and more.