Gif Animation Help

[Alexa5E5A]

I have four frames in my animation that currently go 1>2>3>4>1.  I want them to go 1>2>3>4>3>2>1. How can I do this? Thank you!

[Chuck Uebele]

You would have to duplicate the frames to go in reverse order. 

[Alexa5E5A]

Thank you!!