Database Software

I have a custom workflow, which is getting initiated from a custom form.
For all the notifications which is sent to either an user or a group of users (via roles), how do I show all the history from previous activities.

For example, if there is a request for approval from the preparer, it goes to the VP of that division.
The VP approves and then the notification is sent to the next level which could be for HR approval.
If HR rejects, it goes back to the preparer and the preparer could make the required changes and once again the workflow could be initiated.
Now when the new workflow is initiated, how can I track the history of approval and rejection and show it on the new notifications.

I could not find a way to get the whole history from wf_notifications table, so I started recording all the approval and rejections in a custom table.
Now the question is how to display the custom table action history data on the notification message?

Appreciate all your help.

Regards,

BKN