Hi Nick,
You can achieve the required by going to the below mentioned path:
SPRO-->Sales and Distribution-->Basic Functions-->Pricing-->Pricing Control-->Define Condition Tables
If the required field exists there in this area, then you can directly add it to your customized table and create records for it or you need to create the new field with its technical parameters first before it can be added to the table for further record creation.
Hope this answers your query.
Regards,
Aman