IPFW and icmp

[Dave]

I'm not a master of the internet RFCs, but I do believe icmp messages have
different types.

Now to enable traceroute for IPFW, I might put in a rule like this:

ipfw add pass icmp from any to me

However, how would I make a rule to limit icmp messages to just those used
by traceroute?  Can the messages be distinguished as such?

A dynamic rule that exists only for the duration of a traceroute execution
would be even better.  I take it 'setup' or 'check-state' would follow in
that case?