Yeah, it's possible.
There's a set of addys that regulate milliseconds, seconds, and minutes.
Find the millisecond timer, write a code that's
D - When at xxxx
8 - Changes to yyyy
So if you change from, say 3 milliseconds to 503, it'll cut the seconds in half.
Don't have PJ64, so I can't hack it. But there's a simple solution for someone else to tinker with.
Value Search Base at the beginning of the match.
Let the game go up to 00:05 - 16-bit Value Increased Search
Let the game go up to 00:10 - 16-bit Value Increased Search
Let the game go up to 00:15 - 16-bit Value Increased Search
Let the game go up to 00:20 - 16-bit Value Increased Search
Let the game go up to 00:25 - 16-bit Value Increased Search
Let the game go up to 00:30 - 16-bit Value Increased Search
Let the game go up to 01:05 - 16-bit Value Decreased Search
After a few of those, you'll be able to target the second counter. Right before that is the millisecond (and after, the minutes).