Actionscript error

im following the cartoon smart tutorial for a page flipping book (if that means anything) and im trying to alter the code i have.

the code i have at the moment is on an action layer and is used for a few of my frames which works perfectly and is simply

previous_page.gotoAndStop(1);
current_page.gotoAndStop(2);

however im meant to alter the code so the first frame has this

page = 2;

previous_page.gotoAndStop(page-1);
current_page.gotoAndStop(page);

and the second frame just has

previous_page.gotoAndStop(page-1);
current_page.gotoAndStop(page);

however this throws up errors for all my code “1120: access of undefined proper page”.

i cant work this out as ive followed the video tutorial perfectly yet it dos’nt work…