How can I show an "&" (ampersand) in button or label text?

Try double & (&&). It works with VBA code.

If you are trying to display & in button text, use &&. A single & is used for keyboard shortcuts, and a double ampersand will escape that.

The article Escape ampersand (&) character in C# mentions that you can leave the caption unaltered with single & and just set UseMnemonic property of the button to false.