ActionScript 2.0 :: Multiple Variables (concatenate With Delimiter)?

The course contain ten chapters that all have to report that when a user completed them. When they all are, the status is set
to "completed" for the course. First off the theory behind it:

1. I just completed a chapter.

2. Load a string with then numbers "0,0,0,0,0,0,0,0,0,0", one for each chapter. All 0's, no chapter is completed, all 1's, all chapters are completed, you get the picture.

3. Add a 1 for, lets say chapter 5, would look like this "0,0,0,0,1,0,0,0,0,0".

4. Check if the course is complete, like this: "1,1,1,1,1,1,1,1,1,1", or not.

5. If complete, set status to "complete", if not, set to "incomplete".

In practice:

import flash.external,*;
String(ExternalInterface.call("LMSGetValue, "cmi.suspend_data, TheCourseStatus"));
String(ExternalInterface.call("LMSSetValue, //..add the number "1" to

[code]....

So, after this rant. How do I,

1. Get the string.

2. Add the course number/value to the string

3. Then update the string, and..

4. ..set the appropriate status.

I found out that "I need to concatenate them together with a delimiter so I can separate the string on re-entry", but I don't know how to do that.