Do you have a repeater field in your form? (the field that can add new fields in your form)
If so you will be happy to know that this field can now be used in formulas!
For example, if you want to calculate the total of a given field inside a repeater (like in the example above). You can create a formula like this:
This formula will add up the value of the field 'rnField8' (which in this example is a field inside my repeater)
And that's it now the repeater is going to be used in a formula like in the example below (notice how the total change when you add or modify items in the repeater)