I need to replace a few things in a document.

Like this:

# 45 A needs to become # 45 B
# 78 A needs to become # 78 B
# 102 A needs to become # 102 B

So basically the REPLACE needs to remember what its found in step 1 and put that same string back. So I am asking it, "remember 45" and "remember 78" and put them back in the replace string.