Algorithm problem in sofware project

hey dudes
we're in a middle of a software project, and we got stuck somewhere. in this part we should do something like this:
1. get a rule that looks like !0-4?2-4@@ that defines a password structure, and a dictionary filename
2. break the rule into parts, !0-4 ?2-4 @ @
each part represents an other rule- let's say !0-4 means the first part of the password should contain between 0 and 4 english chars, ?2-4 means that the second part should contain between 2 and 4 general chars (including %,^ etc), and @ means that we receive a word from a dictionary, so let's say the dictionary has the words "abc" and "asd", a good password (that fits in the rule) is alpha%&abcasd, because we can divide it into alph a%& abc asd and it fits the rule.
3. we get an int n (and here's the hard part), we want to generate the n'th password, so that for different n's we'll get different results. in other words, there is a 1 to 1 correspondence between the n's and the passwords generated by the rule.
the problem is that we can get rules like !0-2!0-2, and then the password aa can be generated in 3 different ways- (aa)(), ()(aa), (a)(a). this ofc gets even more complex for longer and more complex rules.

i'd be glad if someone could help us out here...we're really stuck :\

1. Please use correct punctuation and capitalization.
2. I don't understand what you are asking.


Thanks