How can I create an automation that applies a custom border to selected cells?

Hello all. I just got a new job and I work in excel quite a bit.

In this job, I have to download a spreadsheet and select a few cells to highlight with a custom border (just a thick red outline).

I am trying to save myself time and just have a button to press (after selecting my cells) that will apply the boarder but I can't figure out how to do that.

Thanks everyone for your input and have a great day!