It was not clear what exactly you are trying to achieve.
If you are looking for a way to map control values from joystick position to the velocity target values that you send to the motors you may find helpful information in this topic: What do you think is a more efficient way to drive your robot? - #42 by _Colossus
If you are looking for a way to reduce power to the motor when it comes close to the target position in autonomous code, then you need to search forum for PID algorithm examples, like this one Very Simple Very Accurate Chassis Control Code Release
Let us know if you had something else in mind and don’t forget to bookmark V5 online API reference: VEX Help