Copying and pasting multiple sentences in separate location at the same time, holding command?

Ok, I'm sure this used to work and I feel reall stupid but it's driving me mad.

Say there is a paragraph of text and you want to copy the first sentence and the last sentence of paragraph at the same time, to same time - you just hold command right? This doesn't work anymore!

Have I disabled something? How do I fix it? Whenever I hold command now it just doesn't register and copies the most recent sentence highlighted.

Thanks in advance.