Hi, I used to have the same problem. I used to get a really sharp pain in my calves when I walked for even a few minutes.
I just started walking for exercise about two weeks ago. I started by walking 3 km in 35 minutes almost every day. On the days I couldn't go out, I used to jog in place at home. Over just a week I felt a noticeable difference and I didn't get the sharp pain anymore. I think I started to get used to walking that 3 km everyday.
I still get that pain when I jog for more than a few minutes but it's much less than it used to be, and I don't get it at all when I walk anymore. I'm going to be starting C25K to transition into jogging/running in a week or two, but first I'm going to try and get more comfortable with the walking.
My suggestion would be to take it slow. I tried to jog on my first day and I was huffing like a 90 year old 5 minutes into my walk. Once I focused on just doing my walking, I gave my body time to get used to holding its own weight for longer periods.