You've probably already checked out stretches and are doing them, but assuming that you don't have a calf tear, I'd recommend these (scroll down until you get to the calf stretches) and also, try stretching the PF tendon as well.
You could also try wearing a support - I had a problem a few years ago, thought that it might have been a slight tear (turned out not to be) but I had no strength in the calf - couldn't go up on tiptoes. I spent the entire weekend (following discovery) sitting around, doing nothing, wearing a support bandage and RICE-ing a lot. It cleared up after about 2 / 3 weeks and was fine.
Given how close it is to VLM, is it worth seeing a physio?
Good luck, hope it's nothing serious.
