How do you keep foreign plants from growing in a moss garden?

[brittany]

I have moss growing on our rock walkway and we have planted grass close by and seems to want to keep coming up through the moss. I don't think it's hurting it, but it's taking away from the look we are trying to achieve. Any way to keep it from growing? And any way to remove the current plants from the moss without picking out every single plant individually? Any help would be much appreciated. Thanks in advance!