call of duty modern warfare mobilise ds

im currently stuck in the beginning of the game really. umm i got to the part where u hav to type the pin code in to access the computer but im struggling with the code thing. its driving me crazy any tips?

where u have to put in the codes to bypass computer security?
u could try typing numbers into it like this in this order 123 456 789 and if each have yellow in it then slim down ur choices
and btw everytime u fail or start agian the code is dif