Looking for outside reviewer for workbook "proofreading".

I am a consultant who sometimes builds dashboards for nonprofit organizations. I'm realizing that, for more complex workbooks with multiple dashes and many calculations, I sometimes need an outside reviewer to do a final check of results by comparing them to results using the original data sources. I do this myself but need a sort-of proofreader to see if I've missed anything. I'd be interested to hear how others have dealt with this issue and if you know of folks with whom I might subcontract for this service.