Random sampling powershell script for Office 365

I downloaded the random sampling script from Microsoft and am using the online script.  My goal is to be able to pull a random sample of emails from a set of users for someone to review.  No search criteria.  Just random sample of messages from within a specific date range.

(download script here)
http://gallery.technet.microsoft.com/office/Random-Sampling-for-0e761600

the error I'm getting says a parameter cannot be found that matches parameter name 'StartDate'

I think it's because of this last line.

New-MailboxSearch -Name $NameOfSearch -SourceMailboxes $randMBX[0..$totalMBX] -StartDate $StartDate.addminutes($randmins) -EndDate $StartDate.addminutes($randmins + ($totalperiod.totalminutes * $PercentSample *.01)) -TargetMailbox $DiscSearchMBX.alias -SearchQuery $SearchQuery -StatusMailRecipients $StatusMailRecipients

From what I was reading you can't specify a date/time range using New-MailboxSearch script.  Anyone have a way around this?

thanks for your time.