I have been working with C++ (MS .NET) to build Excel
spreadsheets.  I have been able to set values (numeric and
text), change colors, column widths, etc.  However, when I
try to do the following I recieve a COleDispatchException
with no message:

CString str = "Comment";
COleVariant v;
v.bstrVal = str.AllocSysString();
my_range.AddComment(v); // Exception

I also receive an COleDispatchException when I try to Add
a Validation with a string variant formula.

Any help would be appreciated.  Thank you.