How do I join text of expanding cell ranges in a spilt array?

I am creating a daily schedule to assign employees to handle customer calls (C) or emails (E). I want to apply rules to the allocation of C/E within the sheet so managers don't have to make adjustments themselves.

In my WIP schedule there are 4 parts A to D;

• A - Employee data including name, start/finish time, break time, skills etc
• B - Helper 'table' processes rules based on the hour before it and provides a numerical result per hour, per employee
• C - The schedule 'table' allocates Cs to all but the employee with the lowest result who is given Es
• D - Contains the amount to add or subtract for each rule processed within Part B

I've linked a screenshot of a simplified example of the schedule below. Part B has been split showing B1 and B2 to help show what's going on.

The formula within Part B first identifies if the employee is within their working hours, this single formula spills across the entire range encompassing all employees for each hour of the day [B1 in the screenshot].

Now let's say a rule is that each employee is only given 3 hours of Emails (E) each day. The way I planned to do this was for Part B to join the text of all hours up to the hour being processed [B2 in the screenshot], from which the number of Es can be counted. If the number of Es equals 3 then add 10 to that employees 'score'. If the remaining employees have a score of zero then Part C would allocate Es to one of them, and Cs for the employee with the score of 10.

All was going well with other rules until I reached this problem and I think the spilt range from working out if the employees are working that hour is the issue.

The result I want is shown at B2 but what I get is X which joins the text left to right, top to bottom, of the entire range.

I'm aware of the use of @ in Excel 365, however I'm on a Mac OS device and it doesn't play ball. The final product would however run on Windows, but I prefer the Mac setup to do this kind of work on.

Notes:

1. Assume that where two or more scores are the same that the E will be allocated in alphabetical order of employee name,
2. I decided against COUNTIF() as with multiple rules it seemed easier to have one joined-text to process rather than countif this and that,
3. I'd prefer to keep the spilling array as it's a hassle dragging it across numerous columns/rows especially when developing this,
4. No VBA or Macros (forbidden by IT),
5. No volatile functions,
6. This is one option for scheduling among existing software packages, but also the sort of puzzle I enjoy solving, but I met my match with this!

Screenshot:<br>

I have tried a lot of formulas and the closest I've got in isolation does what I want row by row, but the moment I introduce that formula text to the formula producing the spilt array it joins the entire range as shown in X and I cannot find a way to stop that.

For example;

=INDEX(SCAN("",RotaRange,(LAMBDA(a,v,a&v))),1,)

Works fine to drag down over multiple rows, but in the spilled array it joins everything.

I have tried too many combinations to list them but they've included one or more of the following functions in various guises: index(), take(), chooserows(), row(), rows(), hstack(), makearray(), match(), xlookup(), find(), textjoin(), concat(), scan() and more I'm sure.

I've spent more days on this than I care to admit, I've been through SO, Google as you'd expect as well as my own tests and experiments but I can't get past this one!

A REDUCE/SCAN

=LET(range,RotaRange,
    DROP(REDUCE("",SEQUENCE(ROWS(range)),LAMBDA(rRes,rr,
VSTACK(rRes,SCAN("",INDEX(range,rr,0),LAMBDA(sRes,sVal,sRes&sVal))))),1))

Possibly, you will need to drop the last column of RotaRange:

=LET(range,Drop(RotaRange,,-1),
    DROP(REDUCE("",SEQUENCE(ROWS(range)),LAMBDA(rRes,rr,
VSTACK(rRes,SCAN("",INDEX(range,rr,0),LAMBDA(sRes,sVal,sRes&sVal))))),1))