TOPIC: How to discount total including fee fields?

I am hoping this is possible....

I want to have an event which relies on fee fields to calculate payment.

Eg a set of options to pay for a day/half day/week

This works fine and calculates the total cost I want but I want the person registering to pay a deposit only on registering.

I have tried to do this using a percent discount for registered users of the event which would be fine but the discount is only applied to the event cost not the additional fee fields

Is there a way I can do this?

Thanks