I'm sure we can work it out if you can knock up a suitable sample data set. The problem you are facing is that the data you have is already rounded - any algorithm replacing or supplementing the existing one must match its rounding methods.
For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden