If users are just making a single order, or you have a single item, you can:
1. Make the radio button a required field, dropdown probably the best: 'I will be paying by:' [paypal / check]
2. Map the quantity field in paypal connector for your purchase to that field: Quantity: [value from 'I will be paying by:' ] paypal ---> 1 check ----> 0
If no items are being sold (0 quantity) user is not directed to PayPal.
The principle should be about the same, as long as you're not selling multiples of a given item. Each item your selling gets the same 'quantity->0/1' treatment based on the field that has the 'PayPal / Check' field.
Happy to help further, Drew FormAssembly.com Support
Thank you. I ended up making a hidden field for each item sold that multiplied the item quantity by the payment method (1/0) field. I then tied that field to the PayPal connector. That way the correct quantity would be passed to PayPal if that was the method selected. And if they chose check, the paypal quantities would read 0.