The Scan or Libra ability allows the user to view extra information on the enemy, generally it's HP. What I'm going to show you is a basic version of this, but feel free to customise. I've used Rpg maker VX for this, though it should work in RMXP as well, although it proabably won't work in RM2k.
To do this, first set up a 8 variables (I called them all HP) as shown.
There must be eight, since any of eight enemies can be targetted.
Next, You'll need to set up a Scanned State
It expires after one turn, otherwise every time you scan, you'll also recieve information on previously scanned enemies, or those scanned within n turns. This also assumes that only one character will be able to cast scan at any time, otherwise you will find this cumulative effect. Of course, you may prefer this.
If you do decide to not make it go away after one turn, you MUST make KO dispel this effect., otherwise you'll continue to recieve information on dead enemies. Also, since this makes use of an animation to distinguish between multiple enemies, there could be a logic error if the scan state is not dispelled by KO.
Now, onto the Common Event. I've chosen to use the Melee/Physical animation to show which enemy is being targette, but you could just use a new animation that flashes white on the target.
Copy everything from the conditional branch down and paste it seven times. Change the red circled areas to 2, 3, 4, 5, 6, 7 and 8 each time. You should end up with something like this-
Now to actually make the skill. Prepapre an animation for the Scanning(special 1 is perfect for this) and set up the skill as shown.
Again, I've done a few things to customise it, although it is generally preferable for scan to take place once evryone else has had a chance to attack, so a speed deduction is advisable.
Now to see what all this does!