this is not hard to implement. You will need one value for storing the information. Let's say it's a value called password.
Wou would create each button as an object and under every button you would have action adding the current character to the value's string.
Values["password"].String = Values["password"].String .. character
On the delete button you would remove the last character
Values["password"].String = string.sub(Values["password"].String, 1, -2)
And on the cancel you would clear the whole value
Values["password"].String = ""
Then whenever you need it you just compare the value with your password
if Values["password"].String == "4587" then
You also need to figure out displaying the numbers. You could probably use four 10frames animations. Each frame a number from 0 to 9. You could set the current displayed frame based on the pressed button and basedon the number of characters in the string. 2 characters means second slot - second animation.
ActiveAnimation["slot01"].FirstFrame = 2
ActiveAnimation["slot01"].LastFrame = 2
I suppose you could achieve it without coding either but it's just simpler to use the code.