Create A Code That Can Be Called Apon To Activate But Not Receive Or Send Any Information Through The Program?

I have been developing a calculator for complex math. (Much more complicated than +,-,/,*, and above your usual scientific calculator)Its works quite well .In past programs I have used "private functions". I know that you give them a value and it returns on back. But what if you dont want to recive or send value? My example for this is a function I am attempting to make called "Autopi".The idea of Autopi is that whenever a mathimatical operation is about to be performed textbox(s) are cheked to see if they contain pi. (3.14 or 3.141) If they test positive Autopi will continue pi to however many places have been specifyed in the program. (Currently 300 places just beacuse i can :) Before the Autopi function does this it chekes to see if variable "pi" = 1. If it does it proceeds if it doesent its job is done

How would I create a code that can be called apon to activate but not recive or send any information through the program.And just to clarify what I mean by that is it will read information out of a textbox and write into it. But it wont actualy recive anything or send anything back from where it was called apon.