Running Values not working
<p>I am creating a report with Running Value. How do I do A-B=C, C-D=E, E-F=G as show in the image below:</p>

<p><a href="https://i.stack.imgur.com/JjfZD.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/JjfZD.png" alt="image"></a></p>

<p>I tried <code>=Fields!Parent_Amount.Value-RunningValue(Fields!PO_Total_Amount.Value,Sum,"Project_Name")</code> which doesn't work. The section in Yellow is a parent group and blue is a child group.</p>