PC Week reports this week that a Boston-based technology management consulting company has found that an Excel year 2000 error causing drastic math errors went undetected by a handful of Y2K analysis tools.

Unless users of Microsoft Excel download scanning tools from the company's Web site, their spreadsheets could go haywire when they open their files on at New Years Day.

The Y2K bug exists because Excel versions through Excel 2000 have a DATE function that treats all two-digit years as 20th-century dates, regardless of how Excel is configured to handle two-digit dates. As a result, spreadsheets that use the DATE function are particularly vulnerable to Y2K problems.

Compounding the problem is the fact that most Y2K compliance tools don't catch all possible glitches in Excel. Customers checking their Excel spreadsheets for compliance need to be careful to check not only their formulas and macros, but also any user-defined names.

Microsoft officials in Redmond, WA said the company has documented the bug and how the date function is designed to handle four-digit numeric parameters on its Y2K Web page and in Excel Help within the program.