Going to be put on a project that involves making Spreadsheets with old VBA code run on newer versions of excel. Where to get information?

As in getting old excel spreadsheets which presumably were built with VBA6 (or earlier? I dunno yet) to run in Excel10+ (VBA7).

I've never heard of VBA having significant depreciation/legacy issues, but if they do exist, where can I read about them? Drawing a blank on google...