Hi,
Please try to use Measure-Object recipientCount -Sum to count the number of the recipient.
After that you can try to use windows schedual task to run the script every day.
Xiu Zhang
TechNet Community Support
Besides, you can try to use Log Praser to analyze the message tracking log.
Process Tracking Log tool for Exchange Server 2007
b/exchange/archive/2008/02/07/3404839.aspx
Message Tracking tips in Exchange 2007 / Exchange 2010 using CMD lets
b/pepeedu/archive/2010/09/02/message-tracking-cmd-lets-in-exchange-2007-exchange-2010.aspx
How is the issue now? Please feel free to update here.