How can I program the YaBB 1.3.1 to add [+] [-] for each message, so users can vote them?

1.
user Tom, reputation 99, voting power 1
new message from Tom, it's score 0

2.
user Jane, reputation 400, voting power 3
she sets [+] against Tom's message

3.
new message from Tom now score 3 (initial 0 + her voting power)
user Tom, now reputation 102 (his reputation + her voting power)
user Tom, now voting power 2 (for reputation =>100)

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As I understand, I need to add a new value into
/Messages/1234536822.txt
Topic_name|Author|Email|Date-Time|IP|Message||
+Topic_score

And a pair of values into the users' profiles
/Members/tom.dat
+User_reputation = 99
+User_voting_power = 1

Or maybe better a new additional file:
/Messages/1234536822.vot
Jane|3
Dave|4
George|-2

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Can anyone help me? I have a difficulties with Perl and YaBB architecture, my skills better in PHP.

I can made any professional web-design / logo for you in exchange, or pay money if you wish. Thank you!