XDP6 - Is there a way to link/placeholder to charts located in an excel file?

I've tried using a \Graphs folder in the webspace area and placeholdering to exported graph images but when I update the graphs in the specified folder (maintaining filenames), the exported web only seems to show the originally exported file/placeholder image. How do I ensure the placeholder file is always linked?

I cant copy the file as an example due to ITAR/IPR restrictions.