You have to update that field with an own ABAP report, no other way available.
have also a look into this discussion on the same issue from 2008, the user even contacted SAP:
Cycle Counting - Last Cycle count date during Go-Live
You said the material is counted with the first receipt. How do you record this? If you don't, then SAP can't know. It would be good if you could do a posting with MI10 at that moment.