PS action to add text

[bulb763]

I want to create an action that will insert a short text string into a picture, and position it in the bottom right of the image, similar to some images I have seen on here. I want it to scale the text so that it covers the same proportion of the image in a small picture as it does in a large picture.

How on earth do I do this?!

I have seen a tutorial on adding watermarks, which I am sure would be adaptable, but I just do not have a clue how to do this!

Thanks