Try using an 'onclick' rather than an href.
I believe right now, the option to 'drill down' the the actual record in the report is being used first.
But, if you us this format, it will even open in a small pop up window, so you can easily close it and keep working.
"<a onclick=\"var a=window.open('"&[URL for the file]&"', 'newwindow', 'width=700,height=600');\"><img height=\"28\" src=\"
https://images.quickbase.com/si/48/014-view.png\"></a>";
Just replace the "URL" and the img src to match for your use.
(I've not done this exact thing, but it should work)
