Analysis :: Different Aggregation For Different Card Type?

I have a fact, like this

DimCustomerKey, DimCardKey, Amount
1, 1, 20
2, 3, 30
1, 1, 40
3, 4, 50
2, 3, 50

I want a report like this

1, 1, 40
2, 3, 80
3, 4, 50

Logic :

- Each DimCustomerKey has only 1 DimCardKey

- If DimCardKey = 1, reported amount = max(amount)

- If DimcardKey other than 1, reported amount = sum(amount)

How can I implement this with MDX script ?

How can I implement this inside the CUBE (using scope or calculated member etc...)?