Crystal Report to report Monthly Open Incidents

We currently have an Incident Management System to log our Support issues. Incidents have a Created and Closed Date.

I have been asked to write a report that returns all Opened calls grouped by Month for the last 12 months. What I'm having difficult in is working out how to determine whether an Incident was open in one of those months.

Anyone have any ideas?

I'm trying to set this up as a Cross-Tab report with Months listed across the top and totals on 2nd row

Any help would be greatfully received