The problem is that Shipping Method needs to be selected before payment method (because after payment method selection the next step is payment - the total amount depends on shipping method selected).
You don't say what the shipping cost is when other type of payment (not "cash on delivery") and order is
greater than or equal to 100 euro.
If you were to, for example, have only shipping rates: COD is 12 euro , and Credit Card is 10 euro, then this can be done with Payment Director if you are OK showing the payment method name as the shipping method name - i.e. they effectively select the payment method at the same time they select the shipping method:
Setup two Shipping Methods
Cash on delivery shipping
Regular shipping
Setup Shipping Rate Calculation Method "Fixed Rate Shipping" for the above two methods.
Configure
Payment Director to only show COD payment method if they selected "Cash on delivery shipping":
Option Payments.CashOnDelivery ShippingOptionName = "Cash on delivery shipping"
Option Payments.AuthorizeNet ShippingOptionName != "Cash on delivery shipping"
Depending on your requirements for when order is
greater than or equal to 100 euro, you may also need to use
Shipping Director