I have successfully compiled and run some VC++ code that accomplishes what you are trying to do. Actually it looks very similar to your code, so it might just be that the ParameterProperty object needs to be converted to a variant in order to pass it to the NewExecution method. Here is the code from an example on National Instrument's web site:
// Passed arguments must be a container type sequenceArgs = m_engine->NewPropertyObject(TS::PropValType_Container, FALSE, "", 0);
// Create variant to pass to NewExecution method _variant_t sequenceArguments(sequenceArgs, true);
// run the specified sequence in the currently loaded file m_currentExecution = m_engine->NewExecution(m_currentSequenceFile, (const _TCHAR *)sequenceName, modelSeqFile, VARIANT_FALSE, TS::ExecTypeMask_Normal, sequenceArguments);
I have attached a simple MFC Operator Interface that implements this call. Also, you'll find the sequence to call in the zip file.