Rewrite old DOS Cobal prgm into more flexiable Windows Sfw

We have some old line of business cobol (DOS) software that we've used for 25+ years. It's based on some hard coded business assumptions that we want to be redone allowing more flexible yearly constant data input, and to run in a modern windows software environment. It is basically for a process involving the following: input some data, do some table look-ups, apply some math, do some output, maintain some totals for continuation next time; all for multiple clients. Business constants/values should be allowed via table update or excel worksheet updates (not hard coded); output via any standard windows printer with YTD etc totals. All based on YOU decoding current cobol source and reworking into modern but better equivalent. Of course this is all vague until you see what we've got, but assume simplistic current code from a generation ago. This is for a mom+pop operation, not corporate America. So its simpler than you might think as first. Time frame is either now thru Dec 30; or in the spring. You must know how to read an understand old-school cobol; and read thru multiple files of source code to figure out what we're doing - along with in-depth discussion with business owner that has been running this application(s) for 20+ years. We know how we use it, and what we expect from it, but not how it works underneath. We have source and we have running DOS based application files. If you are very confident in your skill set and you're sure you can help, let us know. Due to unknowns - we are specifying a higher than usual budget for the project - to allow room for discussion and enhancements; but we do not expect to go over maximum of this higher budget category.