Stop a tween in the middle of the process

Hello, I have some problems to stop a tween in the middle of the process, for example if someone start another tween that effects the first tween.

I use alpha tween when Im about to show a new content and then if they change content the first content will alpha down to 0 right away.

example:
lets say i have two tabs, “contact us” and “about us” and a person click the “about us” tab they will then trigger this code:
<function to alpha down all other contents>
var tw:Tween = new Tween(aboutc,"_alpha",Strong.easeOut,0,100,1,true);

and if they then click on the “contact us” tab within 1 second they will alpha down the “about us” content but because the tween time isnt up it will come back again. So I need a way to remove the other tween.

I found this code “<tween name>.stop();” but It doesn’t work.