Changing Pokégear background depending on available rematches

I was wondering how it would be possible to change the main background of the Pokégear menu depending on whether or not there were any available rematches.
In this snippet from around line 95 of the script 'PokemonPokegear', I wanted to change the "if" condition to ask if any trainers were awaiting a rematch.

The example line here:

femback=pbResolveBitmap(sprintf("Graphics/Pictures/pokegearbg2"))
[S-HIGHLIGHT]if $Trainer.gender==1 && femback[/S-HIGHLIGHT]
@sprites["background"].setBitmap("Graphics/Pictures/pokegearbg2")
else
@sprites["background"].setBitmap("Graphics/Pictures/pokegearbg")
end

I've attempted this numerous times with different lines of code from the Phone script, but with no luck. I tried changing it to work with [S-HIGHLIGHT]rematchcount[/S-HIGHLIGHT], and the [S-HIGHLIGHT]Trainer[3][/S-HIGHLIGHT] parts, even including the bits that define the aforementioned additions.

So I was wondering if someone could lend me a hand here and help figure this out?
(This is so crazy formal, whaaat. Sorry if I've repeated myself).