I don't know what Flash calls this type of action - if I did - I'd know where to go for help or what to ask for.
So is this a button, a movie?
It's probably an image converted to a movieclip that uses a Tween or two... Try researching the Tween class for whatever version of actionscript you use. A movieclip can be assigned mouse interaction-related code such that clicking on it initiates tweens that change its x and y scale values. Unfortunately, you didn't explain much, so I could only offer a dab of info.
That helps - I just didn't know where to look for how to achieve this procedure.