Dead Reckon

So, long story short, my '77 Delta 88 does not have intermittent wipers, and that frankly, is driving me insane. The wipers themselves work fine, but they work TOO well to simply be left on high or low, and I'm already tired of using the "Mist" function.

So, how hard is it to add intermittent wipers to a car that never had them? I suspect there is a relay tied into the switch position for intermittent wipers. Though I'm not sure, nor do I have access to a parts car to rob this feature from.

I know the guy that invented them pretty much just cobbled together some circuit, and that was in the 60's, so how hard can it be to do to a 1977 Oldsmobile in 2014?

For the record, I don't mind losing my "Low" function if it means intermittent wipers work.