Changing variables inside a csh script

Question

I have a csh script and I have to callenter code here bash script that changes the value of an environment variable, like this:

changevar file:

#!/usr/bin/bash
export FFF=0

beforevar.csh file

#!/bin/csh
setenv FFF 1
echo "BEFORE: " $FFF
./changevar
echo "AFTER: " $FFF

Result:

BEFORE:  1
AFTER:  1

How do I change the FFF variable after, by calling the changevar script?

Thank you