You just need a conditional format expression that references some value that gets changed by your script.
Your script might look like:
Sort Record [no dialog ; restore ]
Set Variable [$$SortOrder ; "First Name" ]
*Refresh Object ["ObjectName of label field here"]
#You may need to refresh several objects here
Your First Name conditional format expression might just be:
$$SortOrder = "First Name"
*Use this if your label text doesn't automatically update to the correct text style. Use the Name box in the Inspector to give layout objects an object name.
Thanks! That works for me.