Nth bar MA

[pj909]

Is there a script to do a Moving Average of every nth bar?
When looking at intraday charts of stats, like $TVOL, I want an MA of the values for 3rd (or 5th or ???) intraday bar for the last 7 days.

I want the MA to be every nth bar but instead it is plotting every bar

[pj909]

/************************************************** ***************
Provided By:
plot a moving average of the nth bar.
for use on an intraday non-price chart like $TVOL i.e.:
show the 11am cumulative average volume for the last nLen days
************************************************** ****************/

var bInit = false;
function preMain() {
setPriceStudy(true);
setStudyTitle("nth Bar MA");
setCursorLabelName("MA", 0);

var fp1 = new FunctionParameter("nLen", FunctionParameter.NUMBER);
fp1.setName("nLen");
fp1.setLowerLimit(1);
fp1.setDefault(7);
var fp2 = new FunctionParameter("nthBar", FunctionParameter.NUMBER);
fp2.setName("nthBar");
fp2.setLowerLimit(1);
fp2.setDefault(3);
}


function main(nLen, nthBar) {

nBarsPerDay = 390 / getInterval();

if (!bInit){
nCnt = nLen * nBarsPerDay
bInit = true;
}

if (close(-nCnt) == null) return;

var vSum = 0;
for(var i = 0; i < nCnt+1; ) {
i = i+nBarsPerDay
vSum += close(-i);
// only sum the nth bar of the day
}

return (vSum / nLen);
}