Cannot figure out how to expand more and etc..

I am trying to find a script or piece of code that will allow me to show more details and colLapse it back afterwards. I have found tons that expand but originally all text is hidden. I don't need that. I need a certain amount of text to be shown and then an expand option for the rest. Here is what I would like:

This is some text. This is some text. This is some text. [...] EXPAND ARROW HERE

Now after the arrow is clicked It would look like this:

This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. COLLAPSE ARROW HERE

How can I do this?

Take a look to the code listed in the link below, most probably will help you start on it:

http://stackoverflow.com/questions/5419482/asp-net-javascript-hide-show-read-more-for-long-text

Good luck!