Hello,
Did you try
anything? You will nearly always get quicker results by trying before posting. Often, what you try will work. If it doesn't work, post what you tried and the problem encountered.
As you have posted no useful info, there won't be much of a useful reply. What little you have posted appears to be impossible. . . How can a field be less than itself. . .
Suggest you post the 2 fields and some sample values and explain what you want the results to be when these sample values are processed.