I would like to merge a few fields in a form into a single hidden field for later use.

In my example, I have employee first name, last name, and employee number.  All of these are separate fields on the form.  

I would like to have a hidden field that merges these three into a single line field.  (i.e LastName, Firstname - Employee Number) to use in a later step in the process (including the dash).

Is this possible?