It looks like you have a lot going on at your other thread, I have not read it all, but would be inclined to say you are dealing with a reproductive disorder. Since you are under vet care, work with your vet on finding the right balance for calcium that your hens may need, but personally, I have found that with reproductive disorders extra calcium is not always the answer since there is an underlying condition at play.
That said...you can use human calcium tablets. 1/2 tablet of Caltrate per day may help, but keep in mind that excess calcium (overload) can cause brittle bones, start damaging the kidney and may in some interfere with the ability to pass eggs easily. While laying hens do need calcium to maintain hard shells and overall health, you can overdo it.
If your hens are eating layer feed and have oyster shell free choice, then I would not supplement extra calcium for more than 2weeks max.