Capturing groups using If then else regular expression construct in java

I have an input string in the following format

String input = "00IG356001110002005064007000000";

Characters 3-7 is the code.

Characters 8-12 is the amount.

Based on the code in the input string (IG356 in the sample input string), i need to capture the amount(00111 in the sample). The value in the amount (characters 8-12) should be picked up only for specific codes and the logic is detailed below.

1. The code should not be SG356. If it is SG356, not a match and exit.

2. a. If the code is not SG356, check if the codes are IG902 or SG350, in this case capture the amount(00111)

   else

   b. Check for the 3 numbers in the code (characters 5-7, 356 in this sample). If they are 200,201,356,370. go ahead and capture the amount

I am using the regular expression shown below: Using positive lookahead and if then else construct.

String regex= ".{2}(?!SG356)((?=IG902|SG350).{5}(.{5}).+|.{2}(?=200|201|356|370).{3}(.{5}).+)";

The regular expression works fine if the code in the input string is IG902 or SG350 (when the 'if' part of the regex is getting matched). but if the 'else' is getting matched, i am unable to capture the amount.

This regular expression is working fine while just checking for a match.

.{2}(?!SG356)((?=IG902|SG350).+|.{2}(?=200|201|356|370).+) 

The problem is only while capturing the group. I am running this in Java. Any help would be greatly appreciated.

The java code i am using is :

public String getTsqlSum(String input, String regex){
     String value = null;
     Matcher m = Pattern.compile(regex).matcher(input);
     System.out.println("Group Count: " + m.groupCount());
     if (m.matches()) {
    for (int i=0;i<m.groupCount();i++){
        System.out.println("For i: " + i +" Value: " + m.group(i));
         }
     }
     return value;
}

public void forumTest(){
    //String input = "00IG902001110002005064007000000";
         String input = "00IG356001110002005064007000000";
    String regex= ".{2}(?!SG356)(?:(?=IG902|SG350).{5}|.{2}(?=200|201|356|370).{3})(.{5}).+";
    System.out.println(match(input, regex));
    String match = getTsqlSum(input, regex);
    System.out.println("Match: " + match);
}