[AS2] How do I Create Object-Orientated Functions?

Hello to all,
I would like to know how to create an object-orientated functions in Actionscript 2. I'm actually not sure if that is what it's called...please correct me if I'm wrong. Anyway here's an example of how I want to be able to call my functions:

PHP Code:

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missile.create(); 


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or

PHP Code:

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missile.fire(); 


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Code:

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missile.create=function(){
//blah blah blah
}

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That's how you would make a function that you could call in that manner.

I'm guessing "missile" is a previously created object, right?

EDIT: What about doing something like this(javascript)

PHP Code:

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cat.prototype.changeName = function(name) {
    this.name = name;
}

firstCat = new cat("pursur")
firstCat.changeName("Bill")
firstCat.talk() //alerts "Bill says meeow!" 


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in Actionscript?