CS4 buttons

Hi everyone,
I’m new to this CS4 world and I can’t make my buttons work…I’m trying to make a portfolio.
I have a button created named “books”. I created a new layer just to insert the AS of that button and to stop the movie clip…the button is inside that movieclip.
Here is what that layer contains:

books.addEventListener(MouseEvent.CLICK, irdiseno);
function irdiseno(event:MouseEvent):void {

The “design” frame is inside that same movieclip…
When I play this it automatically plays the “design” frame when it’s supposed to play when I click the books button.

Here are the errors I get:

“{” expected source: function irdiseno(event:MouseEvent):void {
Unexpected “}” encountered source: }

Hope someone can help me, I need to finish this portfolio ASAP.

I took off the “:void” part and the compiler doesnt show me any errors. But still it doesn’t go to the “design” frame.