Database Software

I want create custom action action History table in PO Approval workflow notification.
My issue is when the action history is too big it doesnot shows complete action history. so i am creating my custom action history table.

But I am able to suppress the standard action history till now.

I have defined an item attribute whose internal name is #history, type is document. I have copied this in the respective message in the workflow.
In the perticular notification go to message-> Edit -> Body-> (Text or HTML)-> there use <BR>&#HISTORY<BR> at the end.

This way we can suppress the standard action history.

But now i want to generate my own custom action history table. I have set the below attribute property and writted a procedure to generate custom action history table
wf_engine.SetItemAttrText(itemtype => p_itemtype,
itemkey => p_itemKey,
aname => 'ACTION_HISTORY',
avalue => 'PACKAGE_NAME.PROCEDURE_NAME/'||p_itemKey);
but still i am not able to get this.

Any suggestion how to get this ??