On the microsoft site I found this page: http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/country.mspx

that talks about using the %systemroot%\System32\Config.nt file to recognize the character set and puncutation, but that's probably not quite what you need. Still, could you write an IF THEN directive to set the DD/MM/YYY or MM/DD/YYYY based on what country code is found?

country

Enables the MS-DOS subsystem to use international time, dates, currency, case conversions, and decimal separators.

Syntax
country=xxx[,[yyy][,[Drive:][Path] FileName]]

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Parameters
xxx : Specifies the Country/Region code.
yyy : Specifies the code page for the Country/Region.
[Drive:][Path] FileName : Specifies the location and name of the file containing Country/Region information.
/? : Displays help at the command prompt.

Hope this helps, although it is certainly stumping me.