Macro reads 3 digit #'s but not 4 digit #'s

Hello,
This is a Macro that was made by Leith Ross which works great for the most part but the problem I am having is it only works if the #'s in A & C are 3 digits (change A2 and C2 to 660 to see what I am talking about) how do I get this macro to work for 4 digit numbers?