This topic has gone off on a(n interesting) tangent. ?
As the OP has Excel I would say automating it would be the best way - if feasible. I’m not sure whether AppleScript automation can get the OP the whole way. I’m more concerned about driving Excel than I am about getting a list of files to work on.
Some of these other tools could be useful. I’ve yet to see evidence that Alfred has much of a role to play here; Somebody educate me if they think it does.
Yes. Hazel, for one, could watch a folder for XLS files and automate converting each one - perhaps with help from Keyboard Maestro. (Alfred, though very nice, isn’t the only Mac automation tool.)