As stated before, this is a problem with the client, not your samba server. I've found that a quick change to the windows client registry solves this problem. Change the following key to 0 (it was set to 1 on my system originally.)
After a quick restart, you should notice that explorer will update automatically. Note: this will result in a slight increase of requests to the samba server (most likely.) Keep that in mind if you are doing this on a large network.