Right click the "ball" symbol in your library, change it's property to MOVIE CLIP
Double click the "ball" symbol, which is now a movie clip, and in the time line insert a keyframe into frame 2
Now change the size of the graphic in this second frame to about 80 %
(-this gives the laser a pulsating effect both where contact is made and in the source layer which follows-)
Insert a Frame into frame 34 of the LASER SOURCE layer
Drag a copy of the "ball" symbol into the first frame of the LASER SOURCE layer and change it's size to 250 %
Centre it on the X axis and leave it about half way up the stage from the line