If I understand you correctly you would need to see the percentage usage of your DHCP address scope where this scope doesn't contain all exclusion you defined on DHCP (like static/reserved addresses).
This is possible if you use following chart:
using this we give you the overview of DHCP scope utilization without all exclusions (note that total amount of IPAddresses is smaller than whole subnet range). Is this what you were talking about?
Thanks, Just what I was looking for.