It may be easiest then to take the report that you really like and just run a Get & Transform step in Excel. @jcole did a presentation on that process that is available on the forum: Get & Transform Part I & II - that would make the changes basically a one-step process.
The file could also be manipulated via python or powershell. I bet you could even put the file into the AI tool of your choice and say write me a NNN (python/powershell) script that transforms refunds from a positive number to a negative number.