Dynamic fields with custom data type

I will try to make this simple. I am using an EBS API and it has a datatype called EGO_ITEM_PUB.ITEM_TBL_TYPE

It is essentially an object which has all of the fields for it's base table (which is MTL_SYSTEM_ITEMS_B).

When using the API, I do something like this...

l_item_table EGO_ITEM_PUB.ITEM_TBL_TYPE;

BEGIN

l_item_table(1).DESCRIPTION := 'TEST';

The above snippet works fine, however my question is this...

Can I somehow dynamically determine the property?

For example...I know the following won't work but I am essentially trying to do something like this (sorry I am not asking my question more clear...it is difficult to phrase it):

l_item_table EGO_ITEM_PUB.ITEM_TBL_TYPE;
v_field_name VARCAHR2(100);

BEGIN

v_field_name := 'DESCRIPTION';

l_item_table(1).v_field_name := 'TEST';

Any ideas?