Customizable Letter Generation: Seeking crm Software for Variable Project Details

Is there a software or mail merge tool capable of generating various letters with distinct fees and content for different projects, for a large amount of letters? For example, if a client requires a 1040 tax return and also needs 1099s due to their business, the letter detailing the work for this client would be different from someone who just needs a 1040 return. I'm currently crafting individual letters for each client one by one based on their specific fees and project types. Is there an intelligent program that can recognize project types, incorporate necessary verbiage, and adjust fees accordingly, while still including standard content for all letters if I have a excel sheet with the fees and project type?