Do you need this to replicate? Because the way you have it set up right now, you’re sending tons of calls over the server/client boundary every time you move your mouse.
The only thing that could relate to this is if you grabbed the inverse of the CFrame, such as
CFrame.new(Vector3.new(1,1,1):inverse() -- as an example
What are you trying to achieve though? Like @anon25856735 said, are you trying to follow your mice position on the screen, or where it’s pointing at in workspace?