How to apply a throttling policy to a group of users

Not sure if this is the right forum but OI nee to know how to apply a throttling policy to  a group of users. The common point is that they are in the same office. I tried creating a shell script using Get-Mailbox and piping the results to a variable and then using the variable but that did not work. Any help would be appreciated.

$var=Get-Mailbox -ResultSize Unlimited | where{$_.Office -eq 'Chicago'}

$var | Set-ThrottlingPolicy -Identity 'PolicyName'