Excel VBA中的多维关联数组

Question

I'm trying to create variable in Excel VBA that contain data like this in 'php'

$classroom['group1']['sub_group1']['John']['math']['pretest'] = 20;
$classroom['group1']['sub_group1']['John']['math']['posttest'] = 50;
$classroom['group1']['sub_group1']['John']['science']['pretest'] = 26;
$classroom['group1']['sub_group1']['John']['science']['posttest'] = 45;

$classroom['group1']['sub_group1']['David']['math']['pretest'] = 40;
$classroom['group1']['sub_group1']['David']['math']['posttest'] = 44;
$classroom['group1']['sub_group1']['David']['science']['pretest'] = 15;
$classroom['group1']['sub_group1']['David']['science']['posttest'] = 17;

$classroom['group1']['sub_group2']['Kate']['math']['pretest'] = 15;
$classroom['group1']['sub_group2']['Kate']['math']['posttest'] = 30;
$classroom['group1']['sub_group2']['Kate']['science']['pretest'] = 26;
$classroom['group1']['sub_group2']['Kate']['science']['posttest'] = 40;

$classroom['group1']['sub_group2']['Alice']['math']['pretest'] = 14;
$classroom['group1']['sub_group2']['Alice']['math']['posttest'] = 35;
$classroom['group1']['sub_group2']['Alice']['science']['pretest'] = 28;
$classroom['group1']['sub_group2']['Alice']['science']['posttest'] = 42;

echo json_encode($classroom);

the result I want it to be should be heirarchy structure as the image below

enter image description here

I tried to use dictionary but my data have duplicated key.

What should I do in order to get the result I want it to be and what kind of variable type should I use?

Thank you.