Recording numeric changes in FTView Studio

There has been a request for me to setup one of our machine HMI's to record a change in a setpoint. It needs to show what the last setpoint was before it was changed. Ex: Current - 310, Last - 305. The system in place is a PanelView Plus 6 which is running with a 1768-L43 Compact Logix. Ive been trying to come up with the best way to do this and tested a few things but i havent got it to work yet.

The reason for this is because operators like to finger the screens when they have issues instead of calling for maintenance support until they make it alot worse. There are already passwords in place to "prevent" this but somehow production always gets them.

Thanks for any help yall can offer.

Do it in the PLC, not the HMI.
Entry value is New_Setpoint
Running value is Current_Setpoint
Last value is Last_Setpoint


If New_Setpoint is in range, then
Last_Setpoint = Current_Setpoint
Current_Setpoint = New_Setpoint.

Thanks for the reply. Im still trying to wrap my head around just putting the logic together to make it happen. Sorry about the way i worded the question. All of our programming is done in the PLC. We only use displays, animation, and momentary contacts on our hmi programming so that whatever machine is running doesnt rely on the HMI being active.

I have come up with how to do it finally. It may not be the best way to do it but it works perfectly for my setup.

If you have v10, it has a built in Audit Feature, which does exactly this. You can even export the report to a csv file. If you don't, as you were.