Unicode strings and Excel 2003

[Sergey Grischenko]

Hello.

As far I know, Excel 2003 maps a Unicode string in an Excel 2003 worksheet
cell to an ASCII byte-string and truncates it before passing it to an XLL
function call. I read about it in Excel SDK and on other web sites devoted
to Excel programming.
At the moment I have a problem with my customer who wants to pass unicode
characters to Excel cells via XLL functions.
The customer insists that the code should work correctly with mutated vowels
(German Umlaut)
in Excel 2003 and Excel 2007. I have no problems with Excel 2007. And I
tried to explain the customer the Excel 2003
restriction but with no success: he insists that he saw such a thing working
somewhere.

Please tell me if it is possible to pass unicode charactes correctly via XLL
in Excel 2003?

Regards,
Sergey Grischenko