Hi everyone, I've been cracking my head trying to translate this cycle and into FP code; so far I haven't had any luck. If anybody can, please help.

*Sample value:
tempCustStr = '50400000019'

****C++ code:******
rhs = 0
for (i = strlen(tempCustStr)-1;i>=0;i--){
digit = *(tempCustStr + i) - '0'
if (i % 2 == 0) {
rhs += digit;
//odd digits
} else {
rhs += (2 * digit) /10 + (2 * digit) % 10;
}
}

rhs = 99 - rhs
checkdigit = rhs / 10
lastdigit = rhs % 10

****My FP code: (It's not working properly)******
rhs = 0
i = LEN(tempCustStr) - 1
DO WHILE i >= 0
digit = VAL(SUBST(tempCustStr,i,1))
IF i % 2 = 0
rhs = rhs + digit
ELSE
rhs = rhs + ((2 * digit)/10) + ((2 * digit) % 10)
ENDIF
i = i - 1
ENDDO

rhs = 99 - rhs
checkdigit = rhs /10
lastdigit = rhs % 10

Thanks a lot, I really appreciate any help

Have a good day,