There seems to be an "off by one error" for the odd/even check. Compare:

from length of string to 1

>for i = strlen( tempCustStr ) to 1 step -1
> ...
> if ( i % 2 = 0 )

from length of (string - 1) to 0

>>for (i = strlen(tempCustStr)-1;i>=0;i--){
...
>> if (i % 2 == 0) {

Therefore in VFP:

if ( i % 2 > 0 )

Also see Paul Vlad Tatavu's message.