The below code should do the job.

xClose = (open+high+low+close)/4
IF BarIndex=0 THEN
xOpen = open
xHigh = high
xLow = low
ELSe
xOpen = (xOpen[1] + xClose[1])/2
xHigh = Max(Max(high, xOpen), xClose)
xLow = Min(Min(low, xOpen), xClose)
ENDIF

harange = xhigh-xlow
habody = abs(xclose-xopen)
test = summation[5](habody>=.2*harange)>0

return test

There you go:

once xOpen = open
xClose     = (open + close + high + low) / 4
if barindex > 0 then
    xOpen  = (xOpen + xClose[1]) / 2
endif
xLow       = min(low,min(xClose,xOpen))
xHigh      = max(high,max(xClose,xOpen))
xRange     = xHigh - xLow
xBody      = abs(xClose - xOpen)
Cond       = xBody >= (xRange * 0.20)    //Body is 20%+ of the range
Result     = summation[5](Cond)
RETURN Result AS "Result"

you asked for “body is 20%”, but his would almost never return a true value, since being exactly 20% is so rare, if not impossible!   So I added >= so that any candle that is equal to or exceeds 20% returns true. Should you want to be returned when the body is <= 20% just replace “>” with “<“.

The returned values are 0 to 5 (0=none, 1…5=the number of candles that match your criterion). With the indicator properties you may select either a line or a histogram.