First step: create the script
It is a modification of a volume aware delete script from here
To spare you the work of the modification I put the modified script here: http://pastebin.com/XRmmKr7R
Copy it to a text editor and save it as del, make it executable
chmod -v 755 /path/tofolder/del
and move it to /usr/bin/.
Now we can create the right click Move to trash option for pcmanfm-mod
First copy the file /usr/share/applications/pcmanfm-user-f6.desktop to ~/.local/share/applications/
Edit this file in second and third line to:Name=Move to TrashSave. Done. When restarting pcmanfm-mod and you right click on a file or folder you want to delete you see the option Move to Trash
Use it and your file will be save in the HOME/.local/share/Trash/files folder.