I do not believe in something magical (unbuildable) that biological cells or human beings have, so with enough technology we could build something that understands just like the brain does. If the brain can do it, nothing stands in the way of something else doing it. Maybe the brain uses for example some quantum mechanics we don't yet fully understand, but we'll still be able to technically use it once we know how, it won't be magically limited to only human brains.
EDIT: ok if the argument is really only about turing machines and that is what is meant by "program", that should be indicated a bit more clearly imho, because computers are not turing machines (nor is the brain), they're less powerful in one way, yet have more features in other ways :)
Maybe you're not clear on what computers are? I strongly encourage you to look up for example the definition of Turing machines. They do not have any "stuff inside"; they consist of a subset of mathematical functions from bitstrings to bitstrings,
A Turing machine is a mathematical function, a subset of (s, [v]) -> [v] that can be generated by the above functions.Mathematical functions are defined as pairs of inputs and outputs. There literally is no "stuff inside" them. They're just sets of (input, output) pairs satisfying left-uniqueness: if (i1, o1) and (i1, o2) are both in the function then o1 = o2 and they were the same pair all along.
Again, Searle is happy that our brains are computers and happy that our brains are conscious. But they are not conscious by virtue of running the right computer program with their computational aspects. In fact, getting you to compute something is relatively hard and unnatural, which is why computers are so great as calculators whereas it takes many years to teach humans the same.