Pending Status Update

Currently I have created a status for tickets where my team is requiring further information. However, when we are dealing with the amount of tickets we receive on a daily basis, its hard to keep an eye on tickets that the customer has replied on. 

I tried to create a trigger so that it would make it easier to identify when a customer has responded to a pending ticket, however when I created the trigger, it would change the status from pending when anyone updated the ticket and not just the customer.

I know from using previous service desks (such as Zendesk) that the pending status made a massive difference in being able to identify customer responses.

Any advice or assistance on this would be greatly appreciated  

Kind Regards
Scott