[JS] Find/Change on all text frames on a single page?

Hi,

Is it possible to perform a .changeGrep() on all text frames on a single page only?

This code gives me "myPageFrames.changeGrep() is not a Function"

var  myPageFrames = myNewPage.textFrames;

     app.findGrepPreferences = app.changeGrepPreferences = null;

     app.findGrepPreferences.findWhat = ".+";

     app.findGrepPreferences.appliedCharacterStyle = myCharStyle;

     app.changeGrepPreferences.changeTo = "myChangetoText";

myFinds = myPageFrames.changeGrep();

Thanks.