Mask&Masked

The first thing you do is you have to create one layer with your text in it. Next you create another layer with your object such as an oval. Then you you right click on your object layer and click on mask, that will automatically change both of your layers. Than you have to create your motion tween in how many frames you want, then you put the motion tween in frame one on the object layer and drag it to the other side. Finally you play your movie and see if it works.