Zend certified PHP/Magento developer

Open a VPN connection with FortiClient from my remote PC to which I connect via OpenVPN

I want to be able to use my desktop at home from my work. I use a laptop at my work and connect via my Synology VPN OpenVPN server to my LAN. After opening the VPN connection I use mstsc (Remote Desktop) to take control of my desktop. Now to be able to reach the network at my work I need to open a VPN connection from my remotely connected desktop using FortiClient SSL. At the moment I do that I loose the remote desktop connection.

For now my solution is to temporarily forward an external port to 3389 on my desktop and connect directly to it. I can then open the FortiClient VPN without further problems but this is not an ideal situation.

How can I configure OpenVPN so that I can open a VPN connection via FortiClient SSL from my desktop at home?