Create time difference between fields

I am trying to calculate the difference in minutes between one autocalculated field to another autocalculated field.  Is this even possible?  I have tried many different codes found online but I am unsure how to reference the specific fields.  This is the autocalc code for both fields:

$.rawValue = Concat(Num2Date(Date(), "M/DD/YY"), " ", Num2Time(Time(), "h:MM"))

Any thoughts?

Thank you!!!