If I'm understanding you correctly you could try making an imagepoint on the torso of the character, and do:
every tick -> set arm position to torso.ImagepointX(insert imagepoint number here), torso.imagepointY (Insert Imagepoint number here).
You will need to make sure that all frames of your animations (On the torso and arms) have the imagepoints you're using set up to ensure it sets position correctly. This may take some tinkering with imagepoints to get the desired look.