Code:
int state = 0;
while{
if buttonA && state == 0
state ++;
if buttonB && state == 1
state ++;
if buttonX && state == 2
state++;
if buttonY && state == 3
state ++;
if buttonBack
state = 0;
if state == 4
{action
state = 0;
}
This is Java-focused pseudocode, but it should be enough to get you started.