The recomendataion for an adult woman is 1000mg of calcium per day. Elderly may require more.
Also, Calcium needs Vitamin D for absorption. If you don't spend time in direct sunlight every couple of days, you should take a vitamin D suppliment.
Also, magnesium is reported to be key in calcium absorption.
Also, iron, such as in spinach and other leafy greens, REDUCES calcium absorption. Since women generally need more iron anyway, it's probably best to stagger calcium intake away from iron/greens, but to keep up any iron rich foods.
Leeks are iron rich too, if you like 'em.
This concludes the broadcast of....
No, I'm not saying you're irratable.
I didn't mean to contradict you.
Please stop beating me.
I know! YOU'VE TOLD ME PERIODS SUCK. STOP HITTING ME.
Er, sorry, I'm sleep deprived. All of that dialogue was made up, though everything from leeks upwards should be true.
If that's ok with you.