Let's begin. Firstly select the rectangle tool.

Click to enlarge

Draw a rectangle as big as the stage. The colour of the fill should be the colour that you want to your spotlight mask to be.

Next select the text tool and type out the text over the box on the stage. Make sure the colour of the text is the colour you want in the final result(of the text).

Create a new layer above the present layer and draw two circles and place them as shown. Be sure to delete the outlines of the circles before placing them.

Click to enlarge

Click to enlarge

Next insert a keyframe at frame no.5 and place the smaller circle right next to the larger one. Make sure there is some distance between them both as shownin the zoomed in image.

Insert a keyframe at frame no.25 and place the larger circle at the end of the text.

Insert another keyframe at frame no.45 and take the larger circle to the same place as it was in frame no.5(I recommend that you should just copy and paste it). Now insert a keyframe at frame no.50 and take the smaller circle to its original place(as in frame no.1). At this point your movie is useless. To get the desired effect we will have to shape tween the top layer(all the KEYFRAMES not frames) and then mask it. Before masking your timeline should look like this-

Click to enlarge

To do the masking bit you will have to right click on the the top layer and select mask. The second layer will automatically be masked if you do it this way.