[Scripting Question] fishing/surfing battle background

Hi to all, there is a way to change the battle background when someone do some action such as fishing or surfing?

if is possible i would can change the battle background when:
-fishing
-fishing while using surf
-surfing
-surfing in a cave

is possible? anyone can help me please?
i use luka's elite battle system https://www.pokecommunity.com/showthread.php?t=343665 )

Surfing and fishing both use the same modifier for battle bases.
It's "enemybase" + (area phrase) + "Water" + (time).png, "playerbase" + (area phrase) + "Water" + (time).png
Area phrase is set as the BattleBack in the map's metadata, and the time is selected from the time of day, though it can be blank.

The wiki has a page about it.

Sorry vendily if that is a stupid post, i have see the wiki but i'm not very well with english and i gave problem to understand the wiki...

If i have correctly understand i must do battleground and call it "battlebgFieldEve.png"... all this?
(I not use base)

Yes, it uses the field backdrop by default.
If you have a map that is only water, you could set the BattleBack Metadata to Water.
The default game comes with examples. The safari zone sets a BattleBack.
And it uses battlebgForest.png, battlebgForestEve.png, or battlebgForestNight.png automatically.

And don't worry about stupid post or not.

sorry Vendily, but i done some wrong and i dont't understand what.
i don't use time sistem (luka's script change color of map and produce time effect).
I have a map, where i have grass, and a lake.
the BattleBack in the map's metadata if battlebgForesta.png; how i must call thee battleback for surfing? thanks