Allocates and returns a copy of m_str via the parameter.
[out] The address of a BSTR in which to return the string allocated by this method.
[out] The address of a VARIANT in which to return the string allocated by this method.
A standard HRESULT value indicating the success or failure of the copy.
After calling this method, the VARIANT pointed to by pvarDest will be of type VT_BSTR.