Found this thought it might be good for other members if i can get it to work anyone can.
1. Update first your Diablo 3 game client by running it normally.
2. Copy the “Diablo III” game folder located in the Program Files or the Program Files (x86) folder to another location.
3. From the “Diablo III” game folder, right click “Diablo III.exe” and select “Create Shortcut“.
4. Copy the shortcut, to a new location accessible to you. (ex. Desktop)
5. Right click on the Shortcut icon, then click on “Properties“.
6. From the “Target” form, add -launch at the end. It should look like this “C:/Program Files (x86)/Diablo III/Diablo III.exe” – 7. -launch
7. Repeat steps 3 to 6, on the other “Diablo III” game folder
8. Open the 2 shortcuts, to run 2 Diablo 3 clients simultaneously.