Checkout Attributes using percentage instead of fixed amount

Hi... is it possible to set up a Checkout Attribute by percentage?.

I need this to allow my customer select if the want to add "shipping inssurace".

Inssurace is 10% of the order subtotal.

I tried with checkout attributes, but is't a fixed amount and i need a percentage...

How could i solve this?....

thanks....

It's not available out of the box.

Shipping Director provides a way to present optional insurance to the customer at time of shipping method selection - see this blog: Customer can add Optional Insurance