セルの取出し
char *charPT;
Range^ xlsxRange;
System::String^ str1;
System::String^ str2;
xlsxRange = (Range^)objSheet->Cells[int row, int colm];
str2 = xlsxRange->Text->ToString();

if ( str2 == nullptr || str2->Length == 0 ) {
return;
}
str1 = xlsxRange->Value[System::Type::Missing]->ToString();
msclr::interop::marshal_context^ context = gcnew msclr::interop::marshal_context();
charPT = ((char*)(context->marshal_as(str1)));   // String→char *
LPCTSTR lpcstr = ((LPCTSTR)(context->marshal_as(str1)));   // String→LPCTSTR
System::Runtime::InteropServices::Marshal::ReleaseComObject(xlsxRange);