MT4 Slow Stochastic indicator

I need a simple modification to a slow stochastic indicator. It is like a 'super slow' stochastic. A normal stochastic uses %K and %D is the 3-period SMA of it. We call this %D as Fast%D A slow stochastic uses Fast%D as it's %K and it's %D is the 3-period SMA of its %K Instead of using a 3-period SMA, I want to use a 3-period smoothing SMA for the slow stochastic.