Well, first, you gotta display the dang thing. I suggest using Custom as the score, but if you have it so that all enemies are invicible you can use kills and custom for something else like lives. If you want them to go through the same path over and over again, use the custom score for the nuetral/computer player who creates the explosions(units created then destroyed right away). For this example, Player 8 is the nuetral comp. Anyway, use these triggers:
First trigger:
Players:
Bounders
Conditions:
Always
Actions:
Show leaderboard for most kills/custom (whichever one you want)
Second:
Players:
Bounders
Conditions:
Current player brings at least 1 men to Bound End
Actions:
Move all men own by Bounders to Bound Start
Add 1 Custom/Kill score To Current player
Add 1 Custom to player 8
Preserve trigger
Those are the triggers for advancing levels, assuming the locations bound end and start are at the proper places. For the bound triggers, just put them under player 8 with the condition "Current player has a Custom score of exactly 1" or whatever for the level you want. Then make one for the next, etc. Remember, the score starts at 0, so if you want it to match the level, make a trigger thats for player 8, always, modify resources for current player: set to 1 custom.
Anyway, thats basically all you need to know in order to make a map like level up bound. Anything else, just ask.