No, can't do that. It is forbidden to have splices inside the wall/ceiling, and every splice must be made up in a UL-approved electrical box and accessible to interior room space. An exception is that an electrical box is allowed if it is placed in an accessible attic space.
I am wondering what if I take the old romex at the wall plug and tape a new piece to it and then pull it from up in the attic to get it to where I have all the romex I need to only make one connection.
Though that would suck if it came apart in the wall.
You could tap into that receptacle (assuming that the circuit has enough available power), cut a hole for adding a new wall switch for the new fan. Cut the romex (power off, of course) about a foot above the cut-out so you have spare Romex. You probably won't be able to pull the remaining Romex down from the attic, because it will be stapled to the studs, so you will likely have to drill the top plate in the attic, and fish a new length of Romex down to the opening for the switch. Then pop in the new box and switch.
Yes, as an alternative, you would be permitted to add an electrical junction box a few feet away from your fan, and just wire in an "extention." Just don't be yankin' on the wire, and make sure the new box is accessible to the attic space.
I could just wack the wire and extend it but I would think that would kinda
be rigging it that would mean I would have two junction boxes with in about two or three feet becouse the total lenght showing is only like two or three feet.
"If you think education is expensive - try ignorance." (Bok's law)