Long Descriptor problem

i'm trying to parse xml in a string that i obtain from bluetooth rfcomm. but im having problems. i tried using HBufC8* iXmlString to receive it as follows, but there's a problem.

Here is the code
void CXmlHandler::StartParsingL( const TDesC& aXmlString )
{
// Remember to cancel any outstanding request first.
if ( IsActive() )
{
Cancel();
}
iXmlString = HBufC8::NewL( aXmlString.Length());
*iXmlString = aXmlString;
iDisplayResult->Des().Zero();
SetActive();

iParser->ParseBeginL();
}

I get the error error C2679: binary '=' : no operator found which takes a right-hand operand of type 'const TDesC' (or there is no acceptable conversion)

any suggestions.