If you mean you want it to go to a area in the code you can use GOTO or GOSUB like this
IF BUTTON()==16 THEN GOTO @LABEL
or
IF BUTTON()==16 THEN GOSUB @LABEL
with GOSUB you need return
GOTO is a one-way trip to some other location in your code.
GOSUB is a temporary visit to some other place in your code. When the RETURN statement is encountered, it'll return to the statement after the GOSUB.
Quick tip: When using BUTTON(), use "AND" instead of "==", so it looks like this:
BUTTON(2) AND 16
This way, even if you are pressing other buttons, it will still see that A was pressed. Using "==" simply gives the value of all buttons being pressed added together.