They are just now moving people off MSO 2003 at ours as well, following complaints from several people that they can't open the newer xlsx, docx, and accdb file extensions. IT and Clinical Analytics are the first wave to move to "brand new" MS Office 2010, as of Jan'13.
Sure hope you aren't doing any life-threatening numerical computations in your version of Excel!
It doesn't matter the version, if 2003 or 2020, I would never do life-threatening computations in Excel. It's just too painful and dangerous (look at how it treates dates). But unfurtunately I don't do this much, I do mostly finance-accounting. Yet, if I did, be sure I would have to put the results in a nicely formatted Excel file.
We got around the inaccuracy problems where I'm at by doing all the sensitive calculations in a more capable program (SAS where I'm at now--R when I consult), then exporting the results to Excel. It avoids most of the problems faced by the poor statistical tools in Excel. It's frustrating to think how difficult it is to cut Excel from the pipeline, but such is the dilemma with Excel being as virulent as it is.
I always found much easier to do all the work in R or Python and then put the results in Excel. Excel is really not a good tool for things that go beyond additions and vlookups.
