Well if you have sprites of bats running around that are all events, you can use an event like this:
For the Bat:
@>Control Variable:[0001]Batquest += 1
"This tells the game data that 0001 gets +1 when the bat is killed"
@>Battle Processing
"This tells the game to start a battle with a "TROOP" of your choosing."
@>Self Switch A = ON
"Turns Self Switch A ON"
New event page
If Self Switch A ON... nothing, with no graphic. (This will make the bat disappear after you kill it.)
Make sure you have hoowever many bats you need on the map.
Now the Questgiver:
@>Show Text: "Clear out my bats from my basement!"
@>Conditional Branch: Variable:[0001]Batquest==5
@>Show Text: "Thank you for clearing my bats out, sonny!"
@> Insert whatever rewards you want here
Else:
@>There are still so many bats, help!!
Hope this helps.