Hmmm ... the version that you have does not include this type of a filter effect, however the FX product includes the ability to load up most any 3rd party AE plug-in filter. And there are a few companies that make a lightning filter that might work for you. You should be able to find something that will meet your need on the toolfarm site.
Digital juice is offering a deal on a plug in set that has electrical arcs. currently it is 1/2 off and is priced around $200. It should work since it is listed on the Boris website. They are half off the Knoll light factory too, in case you need lens flare effects.
Thanks Tony, the only reason I asked was because a "bride" asked for a lightning effect in her wedding video. Unless she is expecting a stormy future I could not see how it would be appropriate. After discussing it with her she decided to change her mind. I did have a laugh when she first asked me though hehe.