How to pass in value to function?

programming flash
1

Hi all,I am new to here and I got a question about how to pass in value to the function.
I am using CS4 and AS2.
This is my code:

attachMovie(“platform”,“platform0”,1);
platform0._x = 300;
platform0._y = 600;
platform0.onEnterFrame = a(0);

function a(num)
{
this._y -= 2;
if(this._y < 800)
{
if (man1.hitTest(this))
{
name = eval(“platfrom”+(num+1));
man1._y = this._y - man1._height;
man1.onPlatform = true;
drop();
}
if (man1._x < this._x-(man1._width/2))
{
man1.onPlatform = false;
drop();
}
if (man1._x+man1._width > this._x + this._width+(man1._width/2))
{
man1.onPlatform = false;
drop();
}
if (this._y < 0)
{
this.removeMovieClip();
}
}
}

I try to pass in this but it fail.
Can anyone help me to solve this question?
Thank you.