Assigned Time to First Reply Time Average Metric

We would like to get a metric that captures the average time from when the conversation was assigned to a team member to the time of their first reply. Assigned Time to First Reply Time average. Some of our customers respond late at night outside of regular business hours and we reply to them on the following day.

Unfortunately, we are unable to use the Average Reply Time metric because it uses the date and time we received the customer's message. Some of our team members show very high Average Reply times even though they respond to customers as soon as the conversations are assigned to them.