I Already installed that plugin, it was called "Fast Upload". I tried by the normal and fast uploading but didn't work.
It seems that I found a trick to make it one-way sync like chizuoka said.
1- disable all your sync including the main folder from the desktop/iOS/android client
2- go to the web create a new folder "Test" in the root of wieyun (The Main Folder)
3- Now create "Test" Folder on your physical drive and put anything you want to upload in it.
4- now go to option and go to the window where you can choose the folder only to sync (follow John's tut. up there) and this only folder will sync.
5- do this procedure whenever you want to upload something and want to delete it from your hard drive
*NOTE*: after syncing complete, you should go to the options again and un-check "Test" folder (That's if you wanted to delete your file without being deleted from the cloud)