Identify spare numbers within a fixed range

A part of my job requires me to identify spare telephone numbers within a spreadsheet from a fixed range. ie the range allocated may be 0191 12200 to 0191 12800. I then need to physically scroll through 600 numbers picking out any spares from within that spreadsheet.
Is it possible to run a query to identify numbers from the allocated range not contained within a spreadsheet?
And if so can anyone give me any pointers on where to start. As you can imagine this is a pain in the backside part of my job.
Any advice would be greatly appreciated