Wanting to add a Custom Field to selected Customers and to print this on Delivery Notes.

Is this possible, I cannot see how at the moment.

The idea is that some customers need specialised deliveries and cannot use standard freight. Coming from MYOB I did this by adding a custom field to the Customers File. This field was added to delivery dockets so when packing it was easily seen that special arrangements were required for freight. 

I see this as a two part problem currently, cannot have a custom field in Customer Details and cannot customise the Delivery form. Am I correct?