Need to study flow control. What is happening is a menu appears with various numbered selections. One of the selections is calibration. If you enter a zero at the menu, then the program skips over everything until it reaches the label named Calibrate_probe. It then runs the calibration code until it gets to the GOTO/ Menu statement. The GOTO/ Menu statement then return the program to the Menu label. The menu appears and then the operator can make another choice.