herculesnetwork on "how to add values of a variable with string, within another variable also string"

add values of a variable with string, within another variable that also contains string, but insert in the middle of the text, eg
I have a text with 100 words, and I have another variable also with a string value, say a word, as I put that word in this text, and text in the center. say there position by 49 or 50 or 51 etc ...Thanks :)