Example:


Line1) Random Text Lamb More Random Text
Line2) Mary had a little Lamb.
Line3) I want Lamb for dinner.
Line4) The Lamb goes moo.

I want to change Lamb to Cow in Line 1 and it would change/update in line 3 and 4 but not Line 2. I want to link certain words in a document to a master word, so when the master word is change, the slave words update to reflect the master word. Like a mirror.
How would i go to achieving this?