How to Take Contribution Form Data and Post to Item Type Metadata

I want to post data from fields I have added in the contribution form add.php file to the Item Type Metadata such as Document Item Type element called "Text" or "Original Format". In the IndexController.php, is their a way to add this to the _processForm function. I thought I could just add another "$elementTexts = array(" like the "Dublin Core" or "Contribution Form", but the element names from "Document" can't be found. I can easily add data from these new fields I added to Dublin Core elements. These new fields are not Dublin Core specific, so I would like to have them show up in elements in the "Document", "Moving Image", "Sound", and "Still Image" Item Types based on the type of contribution they make.

I figured this out. The $elementTexts array name would be "Item Type Metadata". Here is what the code would look like to place a text field from the add.php form called "alttitle" into the "Original Format" element in the Documents Item Type Metadata. Hope this helps others who may have the same question.

'Item Type Metadata'=>array(
'Original Format'=>array(array(