I can't remember if it was here or the other place, but I remember somebody posting a string replace function that worked like:
(strrep "This %%1 will have %%2 new %%3 in it." "string" 3 "words")
And would produce "This string will have 3 new words in it." I was going to make one of my own, but didn't know how to handle a variable number of...variables. I guess I could make the new strings into a list when calling the func.