I am not able to get my sub grid on Account's form

Hi 

all 

my grid name is AXP

I using this code to get sub grid on Account's form but it can not. It is giving me null

var leadwithSameNameGrid = window.parent.document.getElementById("AXP");
var leadwithSameNameGrid = Xrm.Page.getControl("AXP");

This code is working on my dev environment but not in test?