I think it would be a good idea for you to take magnesium-calcium earlier in a day. Try and see how it works out for you. Take 1 capsule, not 2. I think if I took it in the morning, I had a bm by the night time. Give it 10 hours or so, but that's for me. Since you used to be prone to D, I really don't know how fast you will have a bm, but you will have one. Good luck.
-------------------- IBS-C since 2006. No signs of IBS now, it's been 4 yrs. Only dairy allergy now.