I'm not sure why having two filters, one for each column wouldn't give you what you are seeking?
You could concatenate the two fields:
Calculation -> [Field 1] + " - " + [Field 2]
Result -> "Value in Field 1 - Value in Field 2"
Then create a filter on that.
But I think using two separate filters, as John Sobczak said, is a cleaner approach. It also offers more flexibility for your end users.