Change a position of a instanced part that is welded to a players arm, while an anim is playing?

So Im having trouble with this, I tried to create a script that moves the position of a cloned instanced part which is welded to the player rightupperarm while an animations is playing, I tried to Vector3 the position of it, but whenever I tried to do it the instanced part just follows the position and rotation of the rightupperarm, I really need help with this, thank you to anyone who helps me!

You have to manipulate the C0 and C1 Properties of the weld.

e.g.

weld.C0 = weld.C0 * CFrame.Angles(math.rad(90),0,0)