You can use a combination of Custom States, Properties and Custom Events to pretty much do anything you like.
Can you be more specific about what you are trying to do?
Are you trying to show a value on the screen or access the value from a workflow/element on the page-level?
Properties Custom States work very similarly, the main difference being how easily they can be set/accessed.
Custom States - Easily accessed from page-level OR reusable-level elements, however they are more complex to dynamically set.
Properties - Easily dynamically set from the page level and handles Reusable Elements placed in Repeating Groups infinitely better than trying to use custom states, but properties can’t be changed at the Reusable Element level.
Now that we can ‘Return data from custom events’ Custom Events are where the magic can truly happen.
On the page-level you can use the workflow block ‘Trigger a Custom event from a Reusable element’. This will allow you to return anything from the Reusable Element on a page-level workflow.
So what exactly is the magic/processing you need to do and why would you like to put it in a reusable element?