Your only bet is the services like log me in, gotomypc, or an app to run on your PC that will run over an open port, like 80 or 443 (www traffic). VNC is an example. You will have to know what your external public IP address is, and make sure the proper NAT or PAT is in place. If you don't know what you're doing, you're going to open your business up to external security risks. So while there are free resolutions to your problem, you may be setting yourself and you job up for some hacking.