if u get desperate u could probably just try every combination of the numbers 0, 1 and 2 in fields until you find it. you would need to quit mameui each time inbetween changes to the numbers, change the 'ui_joy_up' values in mameui.ini, save, then reload mameui to retest.
so start with ui_joy_up 0,0,0,0 then 0,0,0,1 then 0,0,0,2 then 0,0,1,0 then 0,0,1,1 then 0,0,1,2 and so on (any maths guys here can say how many combinations in total he will need to try?)
