Supplements might help if your body is in need of whatever you supplement with - otherwise you could do more harm than good. Your doctor can order tests (usually a blood sample) to help decide what you need.
You must think the pain is from spasms since you took a muscle relaxer. They don't always work well when taken sporadicly. If it does work it will most likely take several hours to kick in. Spasticity and spasms are something we need to work on EVERY day.
For me, prevention has been more effective than after-the-fact treatment. I've worked with my doctor and PT on a program that includes stretching, rest balanced with activity, and regular dosing with an antispasmodic. Attention to control of body temperature and fatigue helps me avoid both spasticity and weakness.
I still get some spasms but they aren't as frequent or severe. They are much easier to control with an extra baclofen (or maybe a small dose of ativan), extra stretching or a very modest heat application.
Good luck with getting yours under control.
Mary
You might try L-arginine, magnesium and potassium, but I don't know if these would help with MS specific calf pain.