2 Different ways to fade in a MC with AS (1 of them is not working...)

programming flash
1

Hi!
This should be very simple: I want to fade-in a Movieclip (called MC1) using Actionscript.
I normally use this (and it works just fine):

[AS]
this.MC1._alpha = 0;
this.MC1.onEnterFrame = function()
{
if (MC1._alpha <100) {
trace(MC1._alpha);
MC1._alpha +=5;
}
};
[/AS]

However, this time I need to do it without using a function, so I’ve tried the following:
[AS]
this.MC1._alpha = 0;
while (MC1._alpha <100) {
trace(MC1._alpha);
MC1._alpha +=5;
}
[/AS]
Well, even though I can see the alpha values decreasing step by step (throughout the “trace” instruction), the fact is that the MC does not fade-in at all, it’s just starts at a 100% alpha value.
How comes this illogical behaviour? The instruction “trace” shows what it should do, but Flash does not fade it in.
How can I do then what I want?

…this AScript is killing me…!

Thanks for reading,
Manare