variables from flash to flash

i am trying to pass variable from asptesthaifa.swf to category.swf

on the asptesthaifa.swf i have button vith this code

on (release) {
choisvar = "haifa";
getURL("category.swf", "_top", "POST");
}

on the first frame of category.swf
there is code to load choisvar

choisvar = new LoadVars();
choisvar.load("asptesthaifa.swf");

and for testing i trying to use dynamic textbox in the var box i put choisvar

when i load the category page the text box is emoty == no variable been passe

PLEASE HELP