Here is the simplest solution which meets your specifications:
input targetAmount = 0.15;
def newDay = GetDay() <> GetDay()[1];
rec dailyOpen = if newDay then open else dailyOpen[1];
def changeFromOpen = AbsValue(close - dailyOpen);
plot scan = changeFromOpen <= targetAmount;
This solution requires the Study Filter of the scan be set to any intraday time frame but the Extended Hours must be turned off.
Since you specified "Above or Below" and within the target I did not include separate scan signals for "Above and within target" and "Below and within target". This solution simply finds current price within the target range regardless whether the price is above or below the daily open.