well i would think a scale to weigh 0,001g would be more possible as long as you do not have a prof.labratory cause there are plenty of influences which makes it impossible to weigh 0,1mg. even 1mg is not realy reachable without spending hundrets of bugs on a scale. how much money would you like to spend?
otherwise make a solution with f.e. 100ml to 10mg so you have 10/1( 1ml - 0,1mg). just search on the web for a great spoon medium which solute them homogen!! and be realy reasonable with phenazepam.works 40- 60 hours with a dose from 0,4 mg with all the benzo withdrawls in case of depences. check the internet and do not try eye-balling. sorry for my english its not my native language. all the best