3 steps of font-size

Hello, your plugin is great :D, but i have 1 question. Can you make it possible to re-size font in 3-steps? what i mean is to make font normal -> after i click re-size button font size will get bigger by 130% -> again i click button and font will get bigger again to 150%-> and if i click the last time it get smaller to normal size? You know normal, medium and large letters.

Thank you for your support ??