Make parts of mult line field read-only/un-editable?

Make parts of mult line field read-only/un-editable?

Hello, we have a multi line field in one of our data entry apps that pre populates with a "template" of sorts that guides/reminds the user of certain things that must be present in the multi line field. We must use a multi line field because the info varies too much for us to dedicate specific fields for each. 

My question is, is there any way to make certain parts of a multi line un-editable or read-only? Problem we are facing is sometimes users will delete the parts of template on accident or get confused.