Prevent NewItem / Edititem dialog from closing on save OR redirect **dialog** on Save

Before reading further, I am specifically referring to an NewItem.aspx or EditItem.aspx opening up in a SharePoint 2013 dialog box.

At the moment I am opening a "New Item" and/or "Edit Item" list form in a dialog box via custom javascript. What I would like to happen is that, upon the user clicking Save, I want the dialog box not to close, but instead redirect to another page. Just have not been able to get this working... please help!

I've tried linking to the EditItem.aspx / NewItem.aspx with the "&Source=[MY URL]" query string param, but that doesn't work. I've tried doing a redirect via the "onmouseup" on the Save, but that too isn't working. No matter what I am doing, the dialog box continues to close upon save which is not what I want it to do.

This is really getting me quite frustrated.. anyone been able to overcome this?