The old man made no move, changed his expression not at all.

She looked at me, and her face did not change expression.

As I came into the room, he changed his expression quickly and smiled at me.

Her face had not changed expression since the first look of surprise.

The girl beside him, though, did not change her expression.

He had not moved, or changed his expression, watching them both from behind the desk.

It could change expression in a limited way, for instance.

Her face never changed expression, except perhaps to become even cooler.

When Mom turned around, he changed his expression to an innocent smile.

The girl looked at him steadily, her eyes not changing their expression in the least.