Managed C++/CLI

inline void* CThreadSlotData::GetThreadValue(int nSlot)
{
	EnterCriticalSection(&m_sect);
	ASSERT(nSlot != 0 && nSlot < m_nMax);
	ASSERT(m_pSlotData != NULL);
	ASSERT(m_pSlotData[nSlot].dwFlags & SLOT_USED);
	ASSERT(m_tlsIndex != (DWORD)-1);
	if( nSlot <= 0 || nSlot >= m_nMax ) // check for retail builds.
	{
		LeaveCriticalSection(&m_sect);
		return NULL;
	}

	CThreadData* pData = (CThreadData*)TlsGetValue(m_tlsIndex);
	if (pData == NULL || nSlot >= pData->nCount)
	{
		LeaveCriticalSection(&m_sect);
		return NULL;
	}
	void* pRetVal = pData->pData[nSlot];
	LeaveCriticalSection(&m_sect);
	return pRetVal;
}

 private: static System::Decimal MyNumber2;
 private: static System::Decimal DJSubTot = 0;
 private: static System::Decimal DJVATTot = 0;
 private: static System::Decimal DJFreightTot = 0;

 MyNumber2 = 0; 
 if(Decimal::TryParse(textBox8->Text->Trim(), MyNumber2)){
    DJVATTot = MyNumber2;
 }
 MyNumber2 = 0;
if (Decimal::TryParse(textBox9->Text->Trim(), MyNumber2)) {
    if (MyNumber2>0) {
        DJFreightTot = MyNumber2;
    }
}
textBox10->Text = (DJSubTot + DJVATTot + DJFreightTot).ToString();

public ref class My_ProjectData
{
public:
static System::Data::DataTable^ UnitRateTbl = gcnew System::Data::DataTable();

public: static void MyUnitRate_Collect() {
String^ ICode=String::Empty;
for(int W1=0; W1<=UnitRateTbl->Rows->Count-1; W1++){
   ICode=UnitRateTbl->Rows[W1]["itm_code"]->ToString(); // Error on this line UitRateTbl
}
};
Error : function "System::Data::DataRowCollection::default[int]::get" cannot be called with the given argument list

Code: 
private static void SetWIAProperty(IProperties properties, object propName, object propValue)
{
        Property prop = properties.get_Item(ref propName);
        prop.set_Value(ref propValue);
}