how to do conditional calculation with strange requirment

I have strange problem with calculation, and I am not sure what I should do. I have a data that looks like this:

and I need to sort by ID and Date at first,which I did. Then check the oldest day, only if duration for that date is <=0, then I need to calculate usable=current score/earliest date score. so the final results should look like this:

What should I do? How can I check the oldest day and build "usable" to use the score/oldest score?

The codes for sample data are:

ID <-c("1","1","1","1","2","2","2","2")
Date<- c("4/19/2018","7/27/2018","8/24/2018","9/21/2018","10/19/2018","12/14/2018","1/11/2019","1/24/2019")
Duration <- c("-13","86","95","142","2","36","75","81")
score <- c("0.06","0.071","0.054","0.0258","0.0208","0.0448","0.0638","0.0227")

Sample.data <- data.frame(ID, Date, Duration, score)