Creationists often say that they believe that microevolution is a demonstrable,scientific reality whereas macroevolution is a nonsense. By microevolution, they mean that organisms may change to adapt to their environment, but they will never change into an entirely new species. Macroevolution is a nonsense because organisms will never change so much that they will cross that unbreakable wall of separation between species (see? they do believe in unbreakable walls of separation when it suits them!)
Tosh and nonsense, of course. It is like arguing that although I indeed can take one step forward (microstepping, if you like), then because some holy book says that I can’t take more than five steps that means I can’t walk home (microstepping good, macrostepping bad).
But what is even more bizarre is that they aren’t really microevolutionists at all. Look, they believe (say) wolves, hyenas and dogs developed from one representative pair of the dog “kind” that were carried on the Ark.
So, in other words, a mere 4000 years of so-called microevolution is enough to allow all modern day representatives of the dog “kind” to evolve into being from a single ancestral pair. This is not microevolution. Even Richard Dawkins doesn’t believe in evolution on this scale and speed!
In short, the kind of evolution that Creationists believe in is megaevolution, not microevolution.