Throttle Back Mode

In my conveyor system I have what we call a throttle back mode on a conveyor what happens is you can hear and see the belt speed up and slow down. When it comes to the ladder logix in my AB 5000 where would I find this

Where you would find this is completely up to the original programmer.
I would look for a routine with the drive as a title or some routine in your program that handles the speed references for your conveyors. Obviously you have at least a couple different speed set points or some scaled value that is being moved to the drive reference based upon some condition.
It would also help to know if your drive is in the project tree as a drive (Ethernet IP ) or if you are sending the drive an analog signal. It could also be a pre determined set point in the drive based upon what inputs are active to the drive.
There are many ways this could have been set up and you original post does not give nearly enough information to give you an answer.
It may help to zip and post your program, perhaps somebody will look at it for you.

Thanks