ActionScript 2.0 :: Displaying Value From Array In Dynamic Text Box?

i defined a global array in the first frame.When the user clicks on a button a value is inputted into the array, and they can click on several so all the different values are stored in an array.I want to display the last value of the array, so the last button they clicked on, on a separate frame.so i define my array like:

_global.purchases = new Array();

and the code on my button is:

on (release){
_global.purchases="awhite";
_root.gotoAndPlay("checkout_page");
}

and the code on the frame with the text box is:

var arrayCount = purchases.length;
var latestValue = arrayCount-1;
if (purchases[latestValue]=="awhite"){
imagename_txt = "A White";
}

However, the text doesnt display at all. If I trace my array then I get "awhite". If i trace arrayCount I get "6" and "5" for latestValue. But if i try and trace purchases[0] then I get "undefined".