We would like to be able to apply a discount based on the position that the user selects during registration.

We would use this to give a discount to alternates. Teams at our club often have 4 'main' players who play most of the games and pay the normal league fee, and 1 or 2 alternates (5th, 6th) who play fewer games and are charged a much lower fee. The difference between an alternate and a spare is that an alternate is an actual team member and can play in any position, while a spare can only play lead or 2nd.

We can accomplish this discount by creating a custom field, but it would be confusing to the user since they would have to specify that they are an alternate in 2 places (the normal position field and custom field for the discount).