Reverse playing of a movie clip

[font=Comic Sans MS][size=3][color=indigo]Hallo people! This is my first time posting a thread. Hope it works![/color][/size][/font]
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[font=Comic Sans MS][size=3][color=indigo]So, i wanna have a movieclip playing backwards. I use a mask and 2 buttons to go from frame to frame so that the user can move and have the illusion that they are standing in the middle of a panorama.[/color][/size][/font]
[font=Comic Sans MS][size=3][color=indigo]The problem is that i don’t know which actionscript to use in order for the movieclip to go backwards when the user rolls over the right button.[/color][/size][/font]
[font=Comic Sans MS][size=3][color=indigo]hope i explained my problem enough.[/color][/size][/font]
[font=Comic Sans MS][size=3][color=indigo]thanx anyway for every answer.[/color][/size][/font]