How to controll the Alpha speed of a movie clip

Hi every one,

I read a lot of threads in this forum and got a lot of help, thank you.

Here is my question

When a movie clip is clicked on, another movie clip will fade out.

The problem is that the clip that needs to fade out just disapears in a second,
is there a way to controll the speed.

I read a lot of info about this for complicated setups, is there a simple fix for this.
I was hoping I could just do this designR_mc._alpha = 0/4;
But that does not work.

HERE IS THE CODE

design_mc.onRelease = function()
{ designR_mc._alpha =0;

}

Thanks to every one

Adrien