Is there an easy way, short of exporting a list into Excel, to know the number of records that are found in a ‘lookup’?

I’m seeking to know the number of records associated with a single user over a specific time—e.g. a change (+ or -) over a month’s period. 

If I could assess this person’s contacts at the start and end of the month in question, I’d have the information I need for a management report.

Any ideas how to ‘best’ go about determining this information?

Thank you.

Bill