Ubercart

Well, I can't be sure this will work because these modules aren't very well tested....but you are welcome to try a combo of 2 contrib modules I put up.

Attribute Tokens and Custom Price Calculation

The idea behind these was to be extremely flexible and perform things like you are describing without a custom module written for that specific instance.

The custom price module will add a php snippet block to your product where you can add code to be performed during the cart process and Attribute Tokens will give you access to a product's attributes from within that block. So after install of those two modules you should be able to simply add something like this to the custom code field...(assuming you have one attribute called format and 2 options, digital and non-digital and by default you set the item up as shippable)