What I am trying to accomplish is, in a text field I have some string but then I want to concatenate a value that is in a field of the same record

Let say I have a Lead and I open that Lead and within this Lead is a multi-line text field called Greetings.  An in this Greeting text field I have the string "Hello my name is <FirstNameField>" where <FirstNameField> value is pulled from a different field of the same record like First_Name.

Is this possible?