Set font size of button-text

Hey,

I need to customize my buttons in a WDA. I used images which where placed inside the buttons, but I need to change the text of the button dynamically. So I read that I can put a transparent GIF in my buttons. I didn't try it now but even if it works I need to change the font size of the text display in the button.

Is there a way to change that font-size?

Btw. I also tried to use CSS in WDA with Custom Styling For Webdynpro ABAP UI Elements

        but I couldn't figure out where to put the first 4 steps of coding.

I'm very thankful for any hints coming in!