You may just
represent a double value with a
BSTR
, for instance
#include <windows.h>
#include <tchar.h>
#include <sstream>
using namespace std;
int main()
{
wostringstream wos;
double d = 0.57;
wos << d;
BSTR bstr = SysAllocString(wos.str().c_str());
SysFreeString(bstr);
}